Convert CONFIG_SYS_CONSOLE_IS_IN_ENV and CONFIG_CONSOLE_MUX to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_CONSOLE_IS_IN_ENV
   CONFIG_CONSOLE_MUX

Signed-off-by: Simon Glass <sjg@chromium.org>
[trini: Re-order, re-migrate]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/zipitz2_defconfig b/configs/zipitz2_defconfig
index 5899215..8eb9be4 100644
--- a/configs/zipitz2_defconfig
+++ b/configs/zipitz2_defconfig
@@ -1,5 +1,6 @@
 CONFIG_ARM=y
 CONFIG_TARGET_ZIPITZ2=y
+# CONFIG_CONSOLE_MUX is not set
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="$ "