realtek: mdio: rename read/write functions

realtek: mdio: rename read/write functions

Harmonize the read/write functions for better readability. This
aligns with the naming convention of the upstream rtl9300 mdio
driver.

read_phy	-> read_c22
read_phy_mmd	-> read_c45
write_phy	-> write_c22
write_phy_mmd	-> write_c45

Swap order of c22/c45 functions to keep structures sorted
alphabetically.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/23197
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>