ARM: kirkwood: disable dcache for Kirkwood boards

Prior to commit 93b283d49f93 ("ARM: CPU: arm926ejs: Consolidate cache
routines to common file") the kirkwood boards didn't have and dcache
support. The network and usb drivers rely on this. Set
CONFIG_SYS_DCACHE_OFF in the Kirkwood specific config.h.

Reported-by: Leigh Brown <leigh@solinno.co.uk>
Signed-off-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/arch/arm/mach-kirkwood/include/mach/config.h b/arch/arm/mach-kirkwood/include/mach/config.h
index fcd9038..aea6068 100644
--- a/arch/arm/mach-kirkwood/include/mach/config.h
+++ b/arch/arm/mach-kirkwood/include/mach/config.h
@@ -26,6 +26,12 @@
 #define CONFIG_KIRKWOOD_EGIGA_INIT	/* Enable GbePort0/1 for kernel */
 #define CONFIG_KIRKWOOD_RGMII_PAD_1V8	/* Set RGMII Pad voltage to 1.8V */
 #define CONFIG_KIRKWOOD_PCIE_INIT       /* Enable PCIE Port0 for kernel */
+/*
+ * Disable the dcache. Currently the network driver (mvgbe.c) and USB
+ * EHCI driver (ehci-marvell.c) and possibly others rely on the data
+ * cache being disabled.
+ */
+#define CONFIG_SYS_DCACHE_OFF
 
 /*
  * By default kwbimage.cfg from board specific folder is used