net/mlx5: Fix driver load error flow when firmware is stuck

When wait for firmware init fails, previous code would mistakenly
return success and cause inconsistency in the driver state.

Fixes: 6c780a02 ("net/mlx5: Wait for FW readiness before initializing command interface")
Signed-off-by: Gal Pressman <galp@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>