ARM: dma-mapping: convert ARCH_HAS_DMA_SET_COHERENT_MASK to kconfig symbol

The only users of ARCH_HAS_DMA_SET_COHERENT_MASK are 2 ARM platforms:
ixp4xx and pxa cm_x2xx. We've been getting lucky that the define is
implicitly included before dma-mapping.h, but the removal of io.h broke
things (c334bc1 ARM: make mach/io.h include optional). Since memory.h
is the correct place, but no longer exists, convert the define to a
kconfig entry.

Reported-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Imre Kaloz <kaloz@openwrt.org>
Cc: Krzysztof Halasa <khc@pm.waw.pl>
Cc: Eric Miao <eric.y.miao@gmail.com>
Acked-by: Haojian Zhuang <haojian.zhuang@marvell.com>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 31a2ddc..d3999a5 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -180,6 +180,9 @@
 config NEED_DMA_MAP_STATE
        def_bool y
 
+config ARCH_HAS_DMA_SET_COHERENT_MASK
+	bool
+
 config GENERIC_ISA_DMA
 	bool
 
@@ -547,6 +550,7 @@
 config ARCH_IXP4XX
 	bool "IXP4xx-based"
 	depends on MMU
+	select ARCH_HAS_DMA_SET_COHERENT_MASK
 	select CLKSRC_MMIO
 	select CPU_XSCALE
 	select GENERIC_GPIO