omap: consolidate touch screen initialization among different boards

Add common-board-devices.c that will contain the code for peripheral
devices initializatoin shared between multiple boards.
Start small with touchscreen initialization.

Signed-off-by: Mike Rapoport <mike@compulab.co.il>
Signed-off-by: Tony Lindgren <tony@atomide.com>
diff --git a/arch/arm/mach-omap2/Makefile b/arch/arm/mach-omap2/Makefile
index a45cd64..a0c2cae 100644
--- a/arch/arm/mach-omap2/Makefile
+++ b/arch/arm/mach-omap2/Makefile
@@ -270,3 +270,5 @@
 
 disp-$(CONFIG_OMAP2_DSS)		:= display.o
 obj-y					+= $(disp-m) $(disp-y)
+
+obj-y					+= common-board-devices.o