dpll: fix NULL deref in dpll_device_ops() during teardown race

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                    "vendor": "Linux",
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                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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                        "drivers/dpll/dpll_core.c",
                        "drivers/dpll/dpll_netlink.c"
                    ],
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