UAPI: fix endianness conditionals in linux/raid/md_p.h

In the UAPI header files, __BIG_ENDIAN and __LITTLE_ENDIAN must be
compared against __BYTE_ORDER in preprocessor conditionals where these are
exposed to userspace (that is they're not inside __KERNEL__ conditionals).

However, in the main kernel the norm is to check for
"defined(__XXX_ENDIAN)" rather than comparing against __BYTE_ORDER and
this has incorrectly leaked into the userspace headers.

The definition of struct mdp_superblock_s in linux/raid/md_p.h is wrong in
this way.  Note that userspace will likely interpret the ordering of the
fields incorrectly as the big-endian variant on a little-endian machines -
depending on header inclusion order.

[!!!] NOTE [!!!]  This patch may adversely change the userspace API.  It might
be better to fix the ordering of events_hi, events_lo, cp_events_hi and
cp_events_lo in struct mdp_superblock_s / typedef mdp_super_t.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: NeilBrown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>