net/mlx5: Move pci status reg access mutex to mlx5_pci_init

mlx5_pci_init() performs pci specific initialization of the
mlx5_core_dev struct.
Hence move pci_status_mutex to pci initialization routine
mlx5_pci_init().
This allows reusing mlx5_mdev_init() to non PCI devices.

Signed-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Vu Pham <vuhuong@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>