gpio: stp-xway: get rid of the #include <lantiq_soc.h> dependency

Use the xway_stp_{r,w}32 helpers in xway_stp_w32_mask instead of relying
on ltq_{r,w}32 from the architecture specific <lantiq_soc.h>.
This will allow the driver to be compile-tested on all architectures
that support MMIO.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://lore.kernel.org/r/20190702223248.31934-4-martin.blumenstingl@googlemail.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>