MPC512X: Cleanup bus clock names.

Signed-off-by: Grzegorz Bernacki <gjb@semihalf.com>
diff --git a/lib_ppc/board.c b/lib_ppc/board.c
index 6350918..7b95246 100644
--- a/lib_ppc/board.c
+++ b/lib_ppc/board.c
@@ -556,7 +556,7 @@
 	bd->bi_vco     = gd->vco_out;
 #endif /* CONFIG_CPM2 */
 #if defined(CONFIG_MPC512X)
-	bd->bi_ipsfreq = gd->ipb_clk;
+	bd->bi_ipsfreq = gd->ips_clk;
 #endif /* CONFIG_MPC512X */
 #if defined(CONFIG_MPC5xxx)
 	bd->bi_ipbfreq = gd->ipb_clk;