linux/types.h: enable endian checks for all sparse builds

By now, linux is mostly endian-clean. Enabling endian-ness
checks for everyone produces about 200 new sparse warnings for me -
less than 10% over the 2000 sparse warnings already there.

Not a big deal, OTOH enabling this helps people notice
they are introducing new bugs.

So let's just drop __CHECK_ENDIAN__. Follow-up patches
can drop distinction between __bitwise and __bitwise__.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>