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/MPC8572DS_36BIT_defconfig b/configs/MPC8572DS_36BIT_defconfig
index 1f17fa0..1239d08 100644
--- a/configs/MPC8572DS_36BIT_defconfig
+++ b/configs/MPC8572DS_36BIT_defconfig
@@ -8,6 +8,7 @@
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
 CONFIG_BOOTDELAY=10
+# CONFIG_CONSOLE_MUX is not set
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_I2C=y
 CONFIG_CMD_USB=y