x86, MCE, AMD: Replace shared_bank array with is_shared_bank() helper

Use helper function instead of an array to report whether register
bank is shared. Currently only bank 4 (northbridge) is shared.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: http://lkml.kernel.org/r/1363295441-1859-2-git-send-email-boris.ostrovsky@oracle.com


Signed-off-by: Borislav Petkov <bp@suse.de>