IB/core: missing curly braces in ib_find_gid()

Smatch says that, based on the indenting, we should probably add curly
braces here.

Fixes: 03db3a2d

 ('IB/core: Add RoCE GID table management')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>