env: ENV_IS_IN_EXT4 should enable SYS_MMC_ENV_DEV

When enabling CONFIG_ENV_IS_IN_EXT4 the environment might be stored on
an mmc device similar to the CONFIG_ENV_IS_IN_FAT case.

Fixes: 7d080773347c ("Convert CONFIG_SYS_MMC_ENV_DEV et al to Kconfig")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/env/Kconfig b/env/Kconfig
index 451bab4..031cf58 100644
--- a/env/Kconfig
+++ b/env/Kconfig
@@ -655,7 +655,7 @@
 
 config SYS_MMC_ENV_DEV
 	int "mmc device number"
-	depends on ENV_IS_IN_MMC || ENV_IS_IN_FAT || \
+	depends on ENV_IS_IN_MMC || ENV_IS_IN_FAT || ENV_IS_IN_EXT4 || \
 		CMD_MVEBU_BUBT || FMAN_ENET || QE || PHY_CORTINA
 	default 0
 	help