x86/microcode: probe CPU features on microcode update

x86/microcode: probe CPU features on microcode update

Probe for updated CPUID features each time the microcode is
loaded. Specifically this means when the sysfs cpu/microcode
nodes are created (which is when the microcode is first loaded)
or from a user trigger via the sysfs microcode/reload interface.

Orabug: 27878230

Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
(cherry-picked from commit c97a2bf2aa93390b23fbf9adb943e494fee18a18)

conflicts:
  arch/x86/kernel/cpu/microcode/core.c
  arch/x86/include/asm/processor.h

[Backport: call init_scattered_cpuid_features() instead of
 get_cpu_cap().]

Signed-off-by: Brian Maly <brian.maly@oracle.com>