fs/reiserfs/stree.c: remove obsolete __constant

__constant_cpu_to_le32 converted to cpu_to_le32

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Cc: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>