Kernel crash via unchecked inactive-driver testing

NULL dereference in Linux amd_pstate_ut allows local users to crash the kernel by loading the test module on Intel systems. The amd_pstate_ut_init function runs tests without checking whether amd-pstate is active, allowing amd_pstate_ut_check_perf to dereference a NULL pointer. The documented trigger requires the test module to be available and local module-loading privileges; the reported consequence is a kernel oops, not data disclosure or privilege escalation.