arm: mx6: remove unused config variable CONFIG_SPL_NAND_MXS

The config variable CONFIG_SPL_NAND_MXS is only set in
include/configs/imx6_spl.h but used nowhere.
Remove it.

Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
diff --git a/include/configs/imx6_spl.h b/include/configs/imx6_spl.h
index 4598d27..bda9541 100644
--- a/include/configs/imx6_spl.h
+++ b/include/configs/imx6_spl.h
@@ -35,11 +35,6 @@
  */
 #define CONFIG_SPL_PAD_TO		0x11000
 
-/* NAND support */
-#if defined(CONFIG_SPL_NAND_SUPPORT)
-#define CONFIG_SPL_NAND_MXS
-#endif
-
 /* MMC support */
 #if defined(CONFIG_SPL_MMC_SUPPORT)
 #define CONFIG_SYS_MMCSD_FS_BOOT_PARTITION	1
diff --git a/scripts/config_whitelist.txt b/scripts/config_whitelist.txt
index e8f49eb..5b7257b 100644
--- a/scripts/config_whitelist.txt
+++ b/scripts/config_whitelist.txt
@@ -2617,7 +2617,6 @@
 CONFIG_SPL_NAND_INIT
 CONFIG_SPL_NAND_LOAD
 CONFIG_SPL_NAND_MINIMAL
-CONFIG_SPL_NAND_MXS
 CONFIG_SPL_NAND_RAW_ONLY
 CONFIG_SPL_NAND_SIMPLE
 CONFIG_SPL_NAND_SOFTECC