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>

include/common.h

@@ -225,9 +225,6 @@ void	hang		(void) __attribute__ ((noreturn));
 int	timer_init(void);
 int	cpu_init(void);
 
-/* */
-int initdram(void);
-
 #include <display_options.h>
 
 /* common/main.c */