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/xes/xpedite517x/xpedite517x.c b/board/xes/xpedite517x/xpedite517x.c
index e436c28..19b96f6 100644
--- a/board/xes/xpedite517x/xpedite517x.c
+++ b/board/xes/xpedite517x/xpedite517x.c
@@ -58,7 +58,7 @@
 	return 0;
 }
 
-int initdram(void)
+int dram_init(void)
 {
 	phys_size_t dram_size = fsl_ddr_sdram();