board_f: Rename initdram() to dram_init()

This allows us to use the same DRAM init function on all archs. Add a
dummy function for arc, which does not use DRAM init here.

Signed-off-by: Simon Glass <sjg@chromium.org>
[trini: Dummy function on nios2]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/board/amcc/bamboo/bamboo.c b/board/amcc/bamboo/bamboo.c
index 453677a..6a50b39 100644
--- a/board/amcc/bamboo/bamboo.c
+++ b/board/amcc/bamboo/bamboo.c
@@ -438,7 +438,7 @@
 }
 
 
-int initdram(void)
+int dram_init(void)
 {
 	gd->ram_size = spd_sdram();