armv7: ls1021aqds: Set cpo_sample for erratum A-009942

Set cpo_sample as suggested by the driver
"WARN: pls set popts->cpo_sample = 0x58 in <board>/ddr.c to optimize
cpo".

Signed-off-by: York Sun <york.sun@nxp.com>
CC: Shengzhou Liu <Shengzhou.Liu@nxp.com>

board/freescale/ls1021aqds/ddr.c

@@ -96,6 +96,9 @@ found:
 #else
 	popts->cswl_override = DDR_CSWL_CS0;
 
+	/* optimize cpo for erratum A-009942 */
+	popts->cpo_sample = 0x58;
+
 	/* DHC_EN =1, ODT = 75 Ohm */
 	popts->ddr_cdr1 = DDR_CDR1_DHC_EN | DDR_CDR1_ODT(DDR_CDR_ODT_75ohm);
 	popts->ddr_cdr2 = DDR_CDR2_ODT(DDR_CDR_ODT_75ohm);