RDMA/cma: Limit the scope of rdma_is_consumer_reject function

The function is local to cma.c, so let's limit its scope.

Link: https://lore.kernel.org/r/20200413132323.930869-1-leon@kernel.org


Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>