rockchip: gpio: remove dead code

In the following statements
if (a) return a; if (a) return c;
the second return can never be executed.

Identified by cppcheck.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>