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/drivers/net/mpc512x_fec.c b/drivers/net/mpc512x_fec.c
index ad57d56..427e0b8 100644
--- a/drivers/net/mpc512x_fec.c
+++ b/drivers/net/mpc512x_fec.c
@@ -304,7 +304,7 @@
 		 * and do not drop the Preamble.
 		 */
 		out_be32(&fec->eth->mii_speed,
-			 (((gd->ips_clk / 1000000) / 5) + 1) << 1);
+			 (((gd->arch.ips_clk / 1000000) / 5) + 1) << 1);
 
 		/*
 		 * Reset PHY, then delay 300ns