net/mlx5: fw_reset: Don't try to load device in case PCI isn't working

In case PCI reads fail after unload, there is no use in trying to
load the device.

Fixes: 5ec69744

 ("net/mlx5: Add support for devlink reload action fw activate")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>