imx: ddr: imx8m: Move selfref_en after DDR scrub

When doing DDR scrub, the DDR may enter into self refresh if the
selfref_en is enabled before DDR scrub. This will cause scrub
can't complete that SBRSTAT.scrub_done won't be set.

Since the selfref_en can be programmed during the course of
normal operation, move it after DDR scrub

Signed-off-by: Ye Li <ye.li@nxp.com>
Acked-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/drivers/ddr/imx/imx8m/ddr_init.c b/drivers/ddr/imx/imx8m/ddr_init.c
index 99a67ed..b70bcc3 100644
--- a/drivers/ddr/imx/imx8m/ddr_init.c
+++ b/drivers/ddr/imx/imx8m/ddr_init.c
@@ -235,8 +235,6 @@
 
 	/* Step26: Set back register in Step4 to the original values if desired */
 	reg32_write(DDRC_RFSHCTL3(0), 0x0000000);
-	/* enable selfref_en by default */
-	setbits_le32(DDRC_PWRCTL(0), 0x1);
 
 	/* enable port 0 */
 	reg32_write(DDRC_PCTRL_0(0), 0x00000001);
@@ -244,6 +242,9 @@
 
 	board_dram_ecc_scrub();
 
+	/* enable selfref_en by default */
+	setbits_le32(DDRC_PWRCTL(0), 0x1);
+
 	/* save the dram timing config into memory */
 	dram_config_save(dram_timing, CONFIG_SAVED_DRAM_TIMING_BASE);