net/mlx5: Support querying max VFs from device

For ECPF with eswitch manager privilege, query the host max VF count
by querying the device using query_functions command.

With this enhancement:
1. flow steering entries are created only for valid vports based on
   the max VF count of the PF.
2. Driver only queries cap of valid vport.

Eswitch requires the max VFs when doing initialization, so do sr-iov
init before eswitch init.

Signed-off-by: Bodong Wang <bodong@mellanox.com>
Reviewed-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>