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/espresso7420_defconfig b/configs/espresso7420_defconfig
index 0ab0437..22267bb 100644
--- a/configs/espresso7420_defconfig
+++ b/configs/espresso7420_defconfig
@@ -4,8 +4,9 @@
 CONFIG_SYS_MALLOC_F_LEN=0x2000
 CONFIG_IDENT_STRING=" for ESPRESSO7420"
 CONFIG_DEFAULT_DEVICE_TREE="exynos7420-espresso7420"
-# CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_SILENT_CONSOLE=y
+CONFIG_CONSOLE_MUX=y
+# CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_SYS_PROMPT="ESPRESSO7420 # "
 # CONFIG_AUTOBOOT is not set
 # CONFIG_CMD_IMLS is not set