mlx4_core: Fix error flow in the flow steering wrapper

The error flow of the flow steering wrapper had a typo which caused
the wrong firmware command to be called, fix it.

Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>