global: Move from bi_memstart/memsize -> gd->ram_base/ram_size

With the planned removal of bi_memstart & bi_memsize, this patch now
moves the references to the better suiting gd->ram_base/ram_size
variables.

Signed-off-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/powerpc/cpu/mpc85xx/fdt.c b/arch/powerpc/cpu/mpc85xx/fdt.c
index 9569c1a..0d8353c 100644
--- a/arch/powerpc/cpu/mpc85xx/fdt.c
+++ b/arch/powerpc/cpu/mpc85xx/fdt.c
@@ -672,10 +672,10 @@
 		"clock-frequency", get_bus_freq(0), 1);
 #endif
 
-	fdt_fixup_memory(blob, (u64)bd->bi_memstart, (u64)bd->bi_memsize);
+	fdt_fixup_memory(blob, (u64)gd->ram_base, (u64)gd->ram_size);
 
 #ifdef CONFIG_MP
-	ft_fixup_cpu(blob, (u64)bd->bi_memstart + (u64)bd->bi_memsize);
+	ft_fixup_cpu(blob, (u64)gd->ram_base + (u64)gd->ram_size);
 	ft_fixup_num_cores(blob);
 #endif