net/mlx5: Add explicit bar address field

Add bar_addr field to store bar-0 address to avoid calling
pci_resource_start with hard-coded bar-0 as parameter.
Also note that different mlx5 device types will have bar_addr
on different bars.

This patch does not change any functionality.

Signed-off-by: Huy Nguyen <huyn@mellanox.com>
Signed-off-by: Vu Pham <vuhuong@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>