net: stmmac: dwxgmac2: Add support for HW-accelerated VLAN stripping

net: stmmac: dwxgmac2: Add support for HW-accelerated VLAN stripping

This patch adds support for MAC level VLAN tag stripping for the
dwxgmac2 IP. This feature can be configured through ethtool.
If the rx-vlan-offload is off, then the VLAN tag will be stripped
by the driver. If the rx-vlan-offload is on then the VLAN tag
will be stripped by the MAC.

Signed-off-by: Boon Khai Ng <boon.khai.ng@altera.com>
Reviewed-by: Matthew Gerlach <matthew.gerlach@altera.com>
Link: https://patch.msgid.link/20250507063812.34000-4-boon.khai.ng@altera.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>