RDMA/nldev: Fix locking when accessing mr->pd

{
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                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "drivers/infiniband/core/nldev.c",
                        "drivers/infiniband/core/restrack.c",
                        "drivers/infiniband/core/restrack.h",
                        "drivers/infiniband/core/uverbs_cmd.c",
                        "include/rdma/ib_verbs.h"
                    ],
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                }

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "drivers/infiniband/core/nldev.c",
                        "drivers/infiniband/core/restrack.c",
                        "drivers/infiniband/core/restrack.h",
                        "drivers/infiniband/core/uverbs_cmd.c",
                        "include/rdma/ib_verbs.h"
                    ],
                    "versions": [
                        {
                            "version": "4.18",
                            "status": "affected"
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                        {
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                            "versionType": "semver"
                        },
                        {
                            "version": "6.1.188",
                            "lessThanOrEqual": "6.1.*",
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                        {
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                            "versionType": "original_commit_for_fix"
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                }