Convert CONFIG_ENV_IS_IN_SPI_FLASH et al to Kconfig

This converts the following to Kconfig:
   CONFIG_ENV_IS_IN_SPI_FLASH
   CONFIG_ENV_IS_NOWHERE
   CONFIG_ENV_OFFSET
   CONFIG_ENV_OVERWRITE
   CONFIG_ENV_SECT_SIZE
   CONFIG_SYS_MMC_ENV_DEV
   CONFIG_SYS_MMC_ENV_PART

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/imx8ulp_evk_defconfig b/configs/imx8ulp_evk_defconfig
index b8f18c0..129931f 100644
--- a/configs/imx8ulp_evk_defconfig
+++ b/configs/imx8ulp_evk_defconfig
@@ -41,6 +41,7 @@
 CONFIG_CMD_REGULATOR=y
 CONFIG_CMD_EXT4_WRITE=y
 CONFIG_SPL_OF_CONTROL=y
+CONFIG_ENV_OVERWRITE=y
 CONFIG_ENV_IS_IN_MMC=y
 CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG=y
 CONFIG_NET_RANDOM_ETHADDR=y