x86, microcode: Cleanup cpu hotplug notifier callback

Mask out CPU_TASKS_FROZEN bit so that all _FROZEN cases can be dropped.
Also, add some more comments as to why CPU_ONLINE falls through to
CPU_DOWN_FAILED (no break), and for the CPU_DEAD case. Realign debug
printks better.

Idea blatantly stolen from a tglx patch:
http://marc.info/?l=linux-kernel&m=134267779513862



Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Link: http://lkml.kernel.org/r/1344361461-10076-5-git-send-email-bp@amd64.org


Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>