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/freescale/mpc8315erdb/mpc8315erdb.c b/board/freescale/mpc8315erdb/mpc8315erdb.c
index 7779b6d..22f1565 100644
--- a/board/freescale/mpc8315erdb/mpc8315erdb.c
+++ b/board/freescale/mpc8315erdb/mpc8315erdb.c
@@ -222,7 +222,7 @@
 		     CONFIG_SYS_NS16550_CLK / 16 / CONFIG_BAUDRATE);
 	puts("NAND boot... ");
 	timer_init();
-	initdram();
+	dram_init();
 	relocate_code(CONFIG_SYS_NAND_U_BOOT_RELOC + 0x10000, (gd_t *)gd,
 		      CONFIG_SYS_NAND_U_BOOT_RELOC);
 }