am335x: Add pinmux support based on the functions in U-Boot

I was unable to find documentation that said what mode numbers correspond
to what functionality, so I translated over what U-Boot does.

Change-Id: I34fab0f024fa2322d6bb66106aed75224e67354d
Signed-off-by: Gabe Black <gabeblack@chromium.org>
Reviewed-on: http://review.coreboot.org/3489
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
3 files changed