board_f: Drop return value from initdram()

At present we cannot use this function as an init sequence call without a
wrapper, since it returns the RAM size. Adjust it to set the RAM size in
global_data instead, and return 0 on success.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/arch/mips/mach-ath79/dram.c b/arch/mips/mach-ath79/dram.c
index 5ef43a0..1c73add 100644
--- a/arch/mips/mach-ath79/dram.c
+++ b/arch/mips/mach-ath79/dram.c
@@ -9,8 +9,12 @@
 #include <asm/addrspace.h>
 #include <mach/ddr.h>
 
-phys_size_t initdram(void)
+DECLARE_GLOBAL_DATA_PTR;
+
+int initdram(void)
 {
 	ddr_tap_tuning();
-	return get_ram_size((void *)KSEG1, SZ_256M);
+	gd->ram_size = get_ram_size((void *)KSEG1, SZ_256M);
+
+	return 0;
 }