spl_atmel.c: Switch s_init to board_init_f

To facilitate changing lowlevel_init to become s_init, move the current
contents of s_init into board_init_f and add the rest of what
board_init_f does here.
In order to compile clean without CONFIG_SKIP_LOWLEVEL_INIT set, leave an
empty stub of s_init(). It can be removed when lowlevel_init becomes s_init.

Cc: Bo Shen <voice.shen@atmel.com>
Cc: Andreas Bießmann <andreas.devel@googlemail.com>
Tested-by: Matt Porter <mporter@konsulko.com> on sama5d3_xplained
Signed-off-by: Tom Rini <trini@ti.com>
[rebased on current master, leave s_init() as empty stub]
Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>

arch/arm/mach-at91/spl_atmel.c

@@ -70,7 +70,12 @@ __weak void redirect_int_from_saic_to_aic(void)
 	/* This only be used for sama5d4 soc now */
 }
 
+/* empty stub to satisfy current lowlevel_init, can be removed any time */
 void s_init(void)
+{
+}
+
+void board_init_f(ulong dummy)
 {
 	switch_to_main_crystal_osc();
 
@@ -93,4 +98,9 @@ void s_init(void)
 	preloader_console_init();
 
 	mem_init();
+
+	/* Clear the BSS. */
+	memset(__bss_start, 0, __bss_end - __bss_start);
+
+	board_init_r(NULL, 0);
 }