am33xx: move generic parts of pinmux handling out from board/ti/am335x

So they are available for other boards.

Signed-off-by: Peter Korsgaard <peter.korsgaard@barco.com>
diff --git a/arch/arm/cpu/armv7/am33xx/Makefile b/arch/arm/cpu/armv7/am33xx/Makefile
index 7768912..74875b3 100644
--- a/arch/arm/cpu/armv7/am33xx/Makefile
+++ b/arch/arm/cpu/armv7/am33xx/Makefile
@@ -21,6 +21,7 @@
 COBJS	+= ddr.o
 COBJS	+= emif4.o
 COBJS	+= board.o
+COBJS	+= mux.o
 
 SRCS	:= $(SOBJS:.o=.S) $(COBJS:.o=.c)
 OBJS	:= $(addprefix $(obj),$(COBJS) $(COBJS-y) $(SOBJS))