IB/mlx4: Check gid_index return value

IB/mlx4: Check gid_index return value

BugLink: http://bugs.launchpad.net/bugs/1645453
commit 37995116fecfce2b61ee3da6e73b3e394c6818f9 upstream.

Check the returned GID index value and return an error if it is invalid.

Fixes: 5070cd2239bd ('IB/mlx4: Replace mechanism for RoCE GID management')
Signed-off-by: Daniel Jurgens <danielj@mellanox.com>
Reviewed-by: Mark Bloch <markb@mellanox.com>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>