x86/cpu: Remove unnecessary MwAIT leaf checks

The CPUID leaf dependency checker will remove X86_FEATURE_MWAIT if
the CPUID level is below the required level (CPUID_MWAIT_LEAF).
Thus, if you check X86_FEATURE_MWAIT you do not need to also
check the CPUID level.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20241213205030.9B42B458%40davehans-spike.ostc.intel.com