ARM: integrator: allow Integrator to be built with highmem

This fixes Integrator builds with highmem enabled; we need to
translate from 'struct page' to a DMA address, and this is not
possible without __pfn_to_bus().

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-integrator/include/mach/memory.h

@@ -28,5 +28,6 @@
 #define BUS_OFFSET	UL(0x80000000)
 #define __virt_to_bus(x)	((x) - PAGE_OFFSET + BUS_OFFSET)
 #define __bus_to_virt(x)	((x) - BUS_OFFSET + PAGE_OFFSET)
+#define __pfn_to_bus(x)		(((x) << PAGE_SHIFT) + BUS_OFFSET)
 
 #endif