ARM: OMAP: Fix warning in mach-omap2

Fix warning

arch/arm/mach-omap2/timer-gp.c: In function
'omap2_gp_timer_init':
arch/arm/mach-omap2/timer-gp.c:70: warning: implicit
declaration of function 'setup_irq'

Signed-off-by: Dirk Behme <dirk.behme_at_gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/timer-gp.c

@@ -24,6 +24,7 @@
 #include <linux/err.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/irq.h>
 
 #include <asm/mach/time.h>
 #include <asm/arch/dmtimer.h>