printk: Don't WARN on kthread_run failure.

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "kernel/printk/nbcon.c",
                        "kernel/printk/printk.c"
                    ],
                    "versions": [
                        {
                            "version": "76f258bf3f2aae570209319944703a92ac64e29e",
                            "lessThan": "15ba35d632c38d879d182577b0af487de0f2dec4",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "76f258bf3f2aae570209319944703a92ac64e29e",
                            "lessThan": "0af43b52fe4b1751b731c067127fdf47cf1b700c",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "76f258bf3f2aae570209319944703a92ac64e29e",
                            "lessThan": "4e676279798148382497d0e38c0bd51115e64be1",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "76f258bf3f2aae570209319944703a92ac64e29e",
                            "lessThan": "72dd0ec09e7cc98ed58ddeac26575e5d1ab8a93d",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                }

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "kernel/printk/nbcon.c",
                        "kernel/printk/printk.c"
                    ],
                    "versions": [
                        {
                            "version": "6.12",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "6.12",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.12.114",
                            "lessThanOrEqual": "6.12.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.18.57",
                            "lessThanOrEqual": "6.18.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.2.7",
                            "lessThanOrEqual": "7.2.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.3",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }