net: ti: icssg-switch: Add switchdev based driver for ethernet switch support

commit d97051229be4e42774941f23e9028d5dfd29f1e8 from
git://git.ti.com/ti-linux-kernel/ti-linux-kernel.git

commit 972383aecf43c3664750496d5395e669c35ba06e upstream

ICSSG can operating in switch mode with 2 ext port and 1 host port with
VLAN/FDB/MDB and STP offloading. Add switchdev based driver to
support the same.

Driver itself will be integrated with icssg_prueth in future commits

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Xulin Sun <xulin.sun@windriver.com>