ARM: rmobile: Fix rzg2_beacon_defconfig to address new aliases

The resync of the device trees from Linux 5.16-rc3 caused aliases
to appear on the MMC devices which changed the numbering.
This broke the reading/writing of the environmental variables,
so update the defconfig accordingly.

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/configs/rzg2_beacon_defconfig b/configs/rzg2_beacon_defconfig
index b9bbc20..6c48c3b 100644
--- a/configs/rzg2_beacon_defconfig
+++ b/configs/rzg2_beacon_defconfig
@@ -39,7 +39,6 @@
 CONFIG_MULTI_DTB_FIT_USER_DEFINED_AREA=y
 CONFIG_ENV_OVERWRITE=y
 CONFIG_ENV_IS_IN_MMC=y
-CONFIG_SYS_MMC_ENV_DEV=1
 CONFIG_SYS_MMC_ENV_PART=2
 CONFIG_VERSION_VARIABLE=y
 CONFIG_REGMAP=y