Improve error handling in Rockchip SPI drivers

Improve error handling in Rockchip SPI drivers

Merge series from Dragan Simic <dsimic@manjaro.org>:

This is a small series that improves error handling in the probe path
of the Rockchip SPI drivers, by using dev_err_probe() properly in multiple
places.  It also performs a bunch of small, rather trivial code
cleanups, to make the code neater and a bit easier to read.