svcrdma: Remove unused variable in rdma_copy_tail()

Clean up.

linux-2.6/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c: In function
 ‘rdma_copy_tail’:
linux-2.6/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c:376:6: warning:
 variable ‘ret’ set but not used [-Wunused-but-set-variable]
  int ret;
      ^

Fixes: a97c331f ("svcrdma: Handle additional inline content")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>