ARM: OMAP2: Fix compillation error in cm_common

Fixes the following error:
  CC      arch/arm/mach-omap2/cm_common.o
arch/arm/mach-omap2/cm_common.c: In function ‘cm_register’:
arch/arm/mach-omap2/cm_common.c:42:11: error: ‘EINVAL’ undeclared (first use in this function)
arch/arm/mach-omap2/cm_common.c:42:11: note: each undeclared identifier is reported only once for each function it appears in
arch/arm/mach-omap2/cm_common.c:45:11: error: ‘EEXIST’ undeclared (first use in this function)
arch/arm/mach-omap2/cm_common.c: In function ‘cm_unregister’:
arch/arm/mach-omap2/cm_common.c:66:11: error: ‘EINVAL’ undeclared (first use in this function)
make[1]: *** [arch/arm/mach-omap2/cm_common.o] Error 1
make: *** [arch/arm/mach-omap2] Error 2

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/cm_common.c

@@ -13,6 +13,7 @@
 
 #include <linux/kernel.h>
 #include <linux/init.h>
+#include <linux/errno.h>
 
 #include "cm2xxx.h"
 #include "cm3xxx.h"