rockchip: lion-rk3368: defconfig: remove duplicate CONFIG_ENV_IS_IN_MMC

Remove a duplicate CONFIG_ENV_IS_IN_MMC assignment for the lion-rk3368
defconfig.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

configs/lion-rk3368_defconfig

@@ -23,7 +23,6 @@ CONFIG_BOOTSTAGE=y
 CONFIG_SPL_BOOTSTAGE=y
 CONFIG_BOOTSTAGE_REPORT=y
 CONFIG_BOOTSTAGE_FDT=y
-CONFIG_ENV_IS_IN_MMC=y
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_ARCH_EARLY_INIT_R=y
 CONFIG_SPL=y