ARM: zx_defconfig: remove CONFIG_MMC_DW_IDMAC

dw_mmc driver never use this macro, so remove it from
zx_defconfig

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Reviewed-by: Jun Nie <jun.nie@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/configs/zx_defconfig

@@ -83,7 +83,6 @@ CONFIG_MMC=y
 CONFIG_MMC_UNSAFE_RESUME=y
 CONFIG_MMC_BLOCK_MINORS=16
 CONFIG_MMC_DW=y
-CONFIG_MMC_DW_IDMAC=y
 CONFIG_EXT2_FS=y
 CONFIG_EXT4_FS=y
 CONFIG_EXT4_FS_POSIX_ACL=y