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/arch/mips/mach-ath79/dram.c b/arch/mips/mach-ath79/dram.c
index 1c73add..2706812 100644
--- a/arch/mips/mach-ath79/dram.c
+++ b/arch/mips/mach-ath79/dram.c
@@ -11,7 +11,7 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
-int initdram(void)
+int dram_init(void)
 {
 	ddr_tap_tuning();
 	gd->ram_size = get_ram_size((void *)KSEG1, SZ_256M);