[PATCH] md: fix calculation of ->degraded for multipath and raid10

Two less-used md personalities have bugs in the calculation of ->degraded (the
extent to which the array is degraded).

Signed-off-by: Neil Brown <neilb@suse.de>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>