RDMA/qib: Unneeded variable ret

Fix the below warning reported by coccicheck:

drivers/infiniband/hw/qib/qib_file_ops.c:1792:5-8: Unneeded variable:
"ret". Return "0" on line 1876

Link: https://lore.kernel.org/r/20190716172924.GA12241@hari-Inspiron-1545


Signed-off-by: Hariprasad Kelam <hariprasad.kelam@gmail.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>