x86/fpu: Add XFD handling for dynamic states

To handle the dynamic sizing of buffers on first use the XFD MSR has to be
armed. Store the delta between the maximum available and the default
feature bits in init_fpstate where it can be retrieved for task creation.

If the delta is non zero then dynamic features are enabled. This needs also
to enable the static key which guards the XFD updates. This is delayed to
an initcall because the FPU setup runs before jump labels are initialized.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20211021225527.10184-23-chang.seok.bae@intel.com