arm926ejs: add noop implementation for dcache ops

Added noop implementation for dcache operations that will buzz
about missing real implementation and disable the dcache.
This fixes compilation of DaVinci EMAC driver on arm926ejs.

Signed-off-by: Ilya Yanok <yanok@emcraft.com>
diff --git a/arch/arm/cpu/arm926ejs/Makefile b/arch/arm/cpu/arm926ejs/Makefile
index a56ff08..5923e65 100644
--- a/arch/arm/cpu/arm926ejs/Makefile
+++ b/arch/arm/cpu/arm926ejs/Makefile
@@ -26,7 +26,7 @@
 LIB	= $(obj)lib$(CPU).o
 
 START	= start.o
-COBJS	= cpu.o
+COBJS	= cpu.o cache.o
 
 ifdef	CONFIG_SPL_BUILD
 ifdef	CONFIG_SPL_NO_CPU_SUPPORT_CODE