io_uring: rsrc: Optimize return value variable 'ret'

The initialization assignment of the variable ret is changed to 0, only
in 'goto fail;' Use the ret variable as the function return value.

Signed-off-by: Li zeming <zeming@nfschina.com>
Link: https://lore.kernel.org/r/20230317182538.3027-1-zeming@nfschina.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>