ARM: OMAP2: Clean-up mux code

Misc clean-up for the mux code and remove some unnecessary
ifdefs. Patch changes debug function so it can be used on
both 24xx and 34xx.

Changes are mostly for omap2, but patch also cleans up some
omap1 and common mux code.

Signed-off-by: Tony Lindgren <tony@atomide.com>