svcrpc: autoload rdma module

This should fix failures like:

	# rpc.nfsd --rdma
	rpc.nfsd: Unable to request RDMA services: Protocol not supported

Reported-by: Steve Dickson <steved@redhat.com>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>