Kirkwood: dram_init is moved to dram.c

For all Kirkwood boards so far dram_init function is duplicated
dram_init function is moved to dram.c and relevant code from all
board specific files removed

If any board needs specific dram init handling than standard one,
then, a macro CONFIG_SYS_BOARD_DRAM_INIT should be defined in
board config header file and the dram_init function can be put
in board specific source file
For ex. keymile boards

Signed-off-by: Prafulla Wadaskar <prafulla@marvell.com>
diff --git a/include/configs/keymile-common.h b/include/configs/keymile-common.h
index 6c14ca0..62d21f6 100644
--- a/include/configs/keymile-common.h
+++ b/include/configs/keymile-common.h
@@ -85,6 +85,7 @@
 
 #define CONFIG_LOADS_ECHO	1	/* echo on for serial download */
 #define CONFIG_SYS_LOADS_BAUD_CHANGE	1	/* allow baudrate change */
+#define CONFIG_SYS_BOARD_DRAM_INIT	/* Used board specific dram_init */
 
 /*
  * How to get access to the slot ID.  Put this here to make it easy