net: macb: Clean up the .init settings in macb_config instances

net: macb: Clean up the .init settings in macb_config instances

All instances of macb_config currently have the .init field set, but most
of them use macb_init(). In fact, there is no need to duplicate this
across all macb_config instances. Introduce a new macb_init() function
that executes the specific .init if it is set; otherwise, it runs a
default initialization function.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
Link: https://patch.msgid.link/20260310-macb-cleanup-v1-2-928c1a91a7dc@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>