edac: i5000_edac critical fix panic out of bounds

EDAC MC0: INTERNAL ERROR: channel-b out of range (4 >= 4)
Kernel panic - not syncing: EDAC MC0: Uncorrected Error  (XEN) Domain 0 crashed: 'noreboot' set - not rebooting.

This happens because FERR_NF_FBD bit 28 is not updated on i5000.  Due to
that, both bits 28 and 29 may be equal to one, returning channel = 3.  As
this value is invalid, EDAC core generates the panic.

Addresses http://bugzilla.kernel.org/show_bug.cgi?id=14568

Signed-off-by: Tamas Vincze <tom@vincze.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Doug Thompson <dougthompson@xmission.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>