[PATCH] docs: update sparse.txt with CHECK_ENDIAN

Update the sparse documentation to omit the -Wbitwise flag example (as it
is now passed by default), and document the kernel defines to enable
endianness checking.

Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>