ARM: kill off arch_is_coherent

With ixp2xxx removed, there are no platforms that define arch_is_coherent,
so the last occurrences of arch_is_coherent can be removed. Any new
platform with coherent i/o should use coherent dma mapping functions.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
diff --git a/arch/arm/include/asm/barrier.h b/arch/arm/include/asm/barrier.h
index 0511238..8dcd9c7 100644
--- a/arch/arm/include/asm/barrier.h
+++ b/arch/arm/include/asm/barrier.h
@@ -44,10 +44,9 @@
 #define rmb()		dsb()
 #define wmb()		mb()
 #else
-#include <asm/memory.h>
-#define mb()	do { if (arch_is_coherent()) dmb(); else barrier(); } while (0)
-#define rmb()	do { if (arch_is_coherent()) dmb(); else barrier(); } while (0)
-#define wmb()	do { if (arch_is_coherent()) dmb(); else barrier(); } while (0)
+#define mb()		barrier()
+#define rmb()		barrier()
+#define wmb()		barrier()
 #endif
 
 #ifndef CONFIG_SMP