fsl/ddr: Add erratum_a009942_check_cpo and clean related erratum

- add additional function erratum_a009942_check_cpo to check if the
  board needs tuning CPO calibration for optimal setting.
- move ERRATUM_A009942(with revision to check cpo_sample option) from
  fsl_ddr_gen4.c to ctrl_regs.c for reuse on all DDR4/DDR3 parts.
- move ERRATUM_A008378 from fsl_ddr_gen4.c to ctrl_regs.c
- remove obsolete ERRATUM_A004934 which is replaced with ERRATUM_A009942.

Signed-off-by: Shengzhou Liu <Shengzhou.Liu@nxp.com>
[YS: Replaced CONFIG_QEMU_E500 with CONFIG_ARCH_QEMU_E500]
Reviewed-by: York Sun <york.sun@nxp.com>

board/freescale/ls1021aqds/ls1021aqds.c

@@ -22,7 +22,7 @@
 #include <spl.h>
 #include <fsl_devdis.h>
 #include <fsl_validate.h>
-
+#include <fsl_ddr.h>
 #include "../common/sleep.h"
 #include "../common/qixis.h"
 #include "ls1021aqds_qixis.h"
@@ -433,7 +433,9 @@ int board_init(void)
 #ifdef CONFIG_SYS_FSL_ERRATUM_A010315
 	erratum_a010315();
 #endif
-
+#ifdef CONFIG_SYS_FSL_ERRATUM_A009942
+	erratum_a009942_check_cpo();
+#endif
 	major = get_soc_major_rev();
 	if (major == SOC_MAJOR_VER_1_0) {
 		/* Set CCI-400 control override register to