ARM: s3c64xx: enable sparse IRQ support

This is another prerequisite for enabling multiplatform
support, and it is the part I am least certain about.

I assume it will cause the extra boot message "Cannot
allocate irq_descs @ IRQ%d, assuming pre-allocated" to
be printed, but otherwise work ok. This definitely needs
to be tested on real hardware to see if it works.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/mach-s3c64xx/dev-uart.c

@@ -23,6 +23,7 @@
 #include <asm/mach/irq.h>
 #include <mach/hardware.h>
 #include <mach/map.h>
+#include <mach/irqs.h>
 
 #include <plat/devs.h>