ARM: omap: fix prm44xx.c OMAP44XX_IRQ_PRCM build error

When CONFIG_OF is disabled, the compile fails with:

arch/arm/mach-omap2/prm44xx.c:41: error: 'OMAP44XX_IRQ_PRCM' undeclared here (not in a function)
Acked-by: NTony Lindgren <tony@atomide.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-omap2/prm44xx.c

@@ -19,6 +19,7 @@
 
 #include "common.h"
 #include <plat/cpu.h>
+#include <plat/irqs.h>
 #include <plat/prcm.h>
 
 #include "vp.h"