ppc: Move mpc512x clocks to arch_global_data

Move ips_clk and csb_clk into arch_global_data and tidy up.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/powerpc/cpu/mpc512x/ide.c b/arch/powerpc/cpu/mpc512x/ide.c
index dd6b2f4..7a49673 100644
--- a/arch/powerpc/cpu/mpc512x/ide.c
+++ b/arch/powerpc/cpu/mpc512x/ide.c
@@ -100,7 +100,7 @@
 	ide_set_reset(0);
 
 	/* Init timings : we use PIO mode 0 timings */
-	t = 1000000000 / gd->ips_clk;	/* period in ns */
+	t = 1000000000 / gd->arch.ips_clk;	/* period in ns */
 	cfg.bytes.field1 = 3;
 	cfg.bytes.field2 = 3;
 	cfg.bytes.field3 = (pio_specs.t1 + t) / t;