[PARISC] Compile fixups for serial/mux.c

This patch does the following:
* Fixes compiler warnings.
* Replaces a __raw_readl call with the existing macro.

Signed-off-by: Ryan Bradetich <rbrad@parisc-linux.org>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>
1 file changed