MLK-20044 plat: imx8m: fix ddr4 dvfs hang after retention

The RFSHCTL3.refresh_mode should be set normal mode if we
want to disable auto refresh mode.

Signed-off-by: Bai Ping <ping.bai@nxp.com>
(cherry picked from commit 7a2af8801053c087cd0f3a29ac505f4b482933a4)
diff --git a/plat/imx/common/imx8m/ddr4_retention.c b/plat/imx/common/imx8m/ddr4_retention.c
index 509b4a3..ee2e6b6 100644
--- a/plat/imx/common/imx8m/ddr4_retention.c
+++ b/plat/imx/common/imx8m/ddr4_retention.c
@@ -171,7 +171,7 @@
 
 	mmio_write_32(DDRC_PCTRL_0(0), 0x00000001);
 	/* dis_auto-refresh is set to 0 */
-	mmio_write_32(DDRC_RFSHCTL3(0), 0x00000010);
+	mmio_write_32(DDRC_RFSHCTL3(0), 0x00000000);
 
 	/* should check PhyInLP3 pub reg */
 	mmio_write_32(IP2APB_DDRPHY_IPS_BASE_ADDR(0) + 4*0xd0000, 0x0);