Return statements in functions returning bool should use true or false
instead of an integer value.

This code was detected with the help of Coccinelle.
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>