cpu/amd: Correct number of MCA banks cleared

Use the value discovered in the MCG_CAP[Count] for the number of MCA
status registers to clear.  The generations should have the following
number of banks:
 * Family 10h: 6 banks
 * Family 12h: 6
 * Family 14h: 6
 * Family 15h: 7
 * Family 16h: 6

Change-Id: I0fc6d127a200b10fd484e051d84353cc61b27a41
Signed-off-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-on: https://review.coreboot.org/27923
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Martin Roth <martinroth@google.com>
12 files changed