x86/fpu/xsave: Initialize offset/size cache early

Reading XSTATE feature information from CPUID over and over does not make
sense. The information has to be cached anyway, so it can be done early.

Prepare for runtime calculation of XSTATE offsets and allow
consolidation of the size calculation functions in a later step.

Rename the function while at it as it does not setup any features.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220324134623.519411939@linutronix.de