net: sun8i-emac: Add a structure for variant data

net: sun8i-emac: Add a structure for variant data

Currently, EMAC variants are distinguished by their identity, but this
gets unwieldy as more overlapping variants are added. Add a structure so
we can describe the individual feature differences between the variants.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>