Move the family-specific MAC force mode register layout into the switch
configuration. This removes family checks from the RTL83xx link-up path
and converts RTL930x handling to the same field descriptions.
Describe link-state and flow-control force enables separately along with
the fields used to construct resolved MAC state. This allows phylink's
resolved pause settings to remain forced when link state is controlled by
hardware. Add the initial RTL931x link-force description in preparation
for later RTL931x support.
Assisted-by: ChatGPT (OpenAI GPT-5.6 Sol)
Link: https://github.com/openwrt/openwrt/pull/25118
Signed-off-by: Jonas Jelonek <jonas@jonasjelonek.de>