x86/cpu: Use MWAIT leaf definition

The leaf-to-feature dependency array uses hard-coded leaf numbers.
Use the new common header definition for the MWAIT leaf.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/all/20241213205029.5B055D6E%40davehans-spike.ostc.intel.com