realtek: pcs: rtl930x: adjust patch application facilities

realtek: pcs: rtl930x: adjust patch application facilities

Change how patches are applied to reduce redundancy and make the code
more readable. Define a generic function that applies any patch. Within
the RTL930x patch application, define a local macro that helps to get
rid of repeated even/odd checks. While making the code cleaner, it is
also a preparation for further refactoring here.

This adds a local helper macro intended to be only temporary but keeps
the style of the code clean by avoiding a lot of if-else clauses.

Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/22582
Signed-off-by: Robert Marko <robimarko@gmail.com>