Convert CONFIG_SPL_ENV_SUPPORT to Kconfig

Move this option to Kconfig and tidy up existing uses.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/sandbox_spl_defconfig b/configs/sandbox_spl_defconfig
index 108cd6d..ee30e82 100644
--- a/configs/sandbox_spl_defconfig
+++ b/configs/sandbox_spl_defconfig
@@ -1,3 +1,5 @@
+CONFIG_SPL_ENV_SUPPORT=y
+CONFIG_SPL_DRIVERS_MISC_SUPPORT=y
 CONFIG_MMC=y
 CONFIG_SANDBOX_SPL=y
 CONFIG_PCI=y
@@ -17,7 +19,6 @@
 CONFIG_CONSOLE_RECORD=y
 CONFIG_CONSOLE_RECORD_OUT_SIZE=0x1000
 CONFIG_SPL=y
-CONFIG_SPL_DRIVERS_MISC_SUPPORT=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_CPU=y
 CONFIG_CMD_LICENSE=y