x86, mce: print number of MCE banks

The number of MCE banks supported by a CPU is a useful number to know,
so print it out during CPU initialization.

[ Impact: add printout ]

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>