powerpc/8xxx: Improvement to DDR parameters

Changes for P2020DS DDR applies to other 8xxx platform

Signed-off-by: York Sun <yorksun@freescale.com>
diff --git a/arch/powerpc/cpu/mpc8xxx/ddr/options.c b/arch/powerpc/cpu/mpc8xxx/ddr/options.c
index e4805d3..774c0e4 100644
--- a/arch/powerpc/cpu/mpc8xxx/ddr/options.c
+++ b/arch/powerpc/cpu/mpc8xxx/ddr/options.c
@@ -204,6 +204,7 @@
 	 * meet the tQDSS under different loading.
 	 */
 	popts->wrlvl_en = 1;
+	popts->zq_en = 1;
 	popts->wrlvl_override = 0;
 #endif