at91: simplify spl board_init_f function

crt0.S do both memset the bss section and call board_init_r for us, so
remove them from board_init_f().
Signed-off-by: NJosh Wu <josh.wu@atmel.com>
Reviewed-by: NSimon Glass <sjg@chromium.org>
Reviewed-by: NAndreas Bießmann <andreas.devel@googlemail.com>

arch/arm/mach-at91/spl_atmel.c

@@ -98,9 +98,4 @@ void board_init_f(ulong dummy)
 	preloader_console_init();
 
 	mem_init();
-
-	/* Clear the BSS. */
-	memset(__bss_start, 0, __bss_end - __bss_start);
-
-	board_init_r(NULL, 0);
 }