x86: mce: Move per bank data in a single datastructure

This addresses one of the leftover review comments.

Move the per bank data into a single structure. This avoids
several separate variables and also separate allocation of sysfs objects.

I didn't move the CMCI ownership information so far because
that would have needed some non trivial changes in the algorithms.

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