x86/fpu: Add sanity checks for XFD

Add debug functionality to ensure that the XFD MSR is up to date for XSAVE*
and XRSTOR* operations.

 [ tglx: Improve comment. ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211021225527.10184-16-chang.seok.bae@intel.com