realtek: overwrite c22 polling unconditionally on RTL930x

realtek: overwrite c22 polling unconditionally on RTL930x

During setup the mdio driver decides the polling mode of the 4 smi
busses depending on the DTS phy settings. This works as follows:

- set polling to c45 if at least one phy is ethernet-phy-ieee802.3-c45
- set polling to c22 if all phys are ethernet-phy-ieee802.3-c22

On RTL930x it is not possible to switch to c22 if uboot has set c45
before. Fix this by overwriting the bitfield properly. While we are
here:

- Sort variables according to kernel style (inverse christmas tree)
- Initialize fields properly with  = { 0 }
- Use GENMASK() for better readability
- Make use of RTMDIO_MAX_SMI_BUS

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/19161
Signed-off-by: Robert Marko <robimarko@gmail.com>