fs/ntfs3: Use enum req_op where appropriate

Improve static type checking by using enum req_op instead of u32 for
block layer request operations.

Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20220714180729.1065367-60-bvanassche@acm.org


Signed-off-by: Jens Axboe <axboe@kernel.dk>