ARM: gemini: fix the gemini build

Test-compiling obscure machines I notice that the gemini (which
by the way lacks a defconfig) is broken since some time back.
Adding a simple missing include makes it build again.
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NOlof Johansson <olof@lixom.net>

arch/arm/mach-gemini/irq.c

@@ -17,6 +17,7 @@
 #include <linux/sched.h>
 #include <asm/irq.h>
 #include <asm/mach/irq.h>
+#include <asm/system_misc.h>
 #include <mach/hardware.h>
 
 #define IRQ_SOURCE(base_addr)	(base_addr + 0x00)