realtek: mdio: convert to generic regmap_bulk_write()

realtek: mdio: convert to generic regmap_bulk_write()

Each architecture has its own SMI address and SMI data size. Make the
current device specific coding generic by

- adding SMI start address and SMI data size to configuration structure
- moving regmap_bulk_write() over to the generic rtmdio_run_cmd()
- deleting all device specific rtmdio_xxxx_run_cmd() versions

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/23092
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>