Fix some issues found by clang

Fix some issues found by clang

The clang compiler complained about each of these.

The mdmon.h error will only affect 'far' RAID10 arrays using intel or DDF
metadata, and there is no such thing.

The mdopen.c will cause a problem if there are no free md device
numbers in the first 512.  That is fairly unlikely.

The restripe.c error would only affect the 'test_stripe' command, and
probably doesn't change its behaviour.

The super-intel.c fix is purely cosmetic.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>