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/cpu.c b/arch/powerpc/cpu/mpc512x/cpu.c
index a1a3bd4..641120f 100644
--- a/arch/powerpc/cpu/mpc512x/cpu.c
+++ b/arch/powerpc/cpu/mpc512x/cpu.c
@@ -68,7 +68,7 @@
 	}
 	printf ("at %s MHz, CSB at %s MHz (RSR=0x%04lx)\n",
 		strmhz(buf1, clock),
-		strmhz(buf2, gd->csb_clk),
+		strmhz(buf2, gd->arch.csb_clk),
 		gd->reset_status & 0xffff);
 	return 0;
 }