vdpa/mlx5: update MAC address handling in mlx5_vdpa_set_attr()

vdpa/mlx5: update MAC address handling in mlx5_vdpa_set_attr()

Improve MAC address handling in mlx5_vdpa_set_attr() to ensure that
old MAC entries are properly removed from the MPFS table before
adding a new one. The new MAC address is then added to both the MPFS
and VLAN tables.

This change fixes an issue where the updated MAC address would not
take effect until QEMU was rebooted.

Signed-off-by: Cindy Lu <lulu@redhat.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260126094848.9601-4-lulu@redhat.com>