realtek: pcs: fix sds_config struct definition

realtek: pcs: fix sds_config struct definition

In kernel coding style, it is highly disregarded to hide structures
behind typedefs ([1]). The PCS driver still contains a typedef for the
sds_config which was taken over from the PHY driver.

- drop the typedef, just declaring it as a struct
- give it the common 'rtpcs_' prefix
- adjust all usage locations

[1] https://www.kernel.org/doc/html/v6.18/process/coding-style.html#typedefs

Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/21410
Signed-off-by: Robert Marko <robimarko@gmail.com>