ARM: OMAP2/3: Reorganize Makefile to add omap4 support

We don't necessarily want to compile in irq.o and sdrc.o for omap4.
Also, clock and prcm may not be implemented initially.
Signed-off-by: NTony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/Makefile

@@ -3,9 +3,14 @@
 #
 
 # Common support
-obj-y := irq.o id.o io.o sdrc.o control.o prcm.o clock.o mux.o \
-		devices.o serial.o gpmc.o timer-gp.o powerdomain.o \
-		clockdomain.o
+obj-y := id.o io.o control.o mux.o devices.o serial.o gpmc.o timer-gp.o
+
+omap-2-3-common				= irq.o sdrc.o
+prcm-common				= prcm.o powerdomain.o
+clock-common				= clock.o clockdomain.o
+
+obj-$(CONFIG_ARCH_OMAP2) += $(omap-2-3-common) $(prcm-common) $(clock-common)
+obj-$(CONFIG_ARCH_OMAP3) += $(omap-2-3-common) $(prcm-common) $(clock-common)
 
 obj-$(CONFIG_OMAP_MCBSP) += mcbsp.o