These form the basis of the basic WRITE etc primitives, so we
need them to be always visible. Otherwise we see errors like:
mm/filemap.c:2164: error: 'REQ_WRITE' undeclared
fs/read_write.c:362: error: 'REQ_WRITE' undeclared
fs/splice.c:1108: error: 'REQ_WRITE' undeclared
fs/aio.c:1496: error: 'REQ_WRITE' undeclared
Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>