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/p2771-0000-500_defconfig b/configs/p2771-0000-500_defconfig
index 28160c2..1633ed2 100644
--- a/configs/p2771-0000-500_defconfig
+++ b/configs/p2771-0000-500_defconfig
@@ -3,6 +3,7 @@
 CONFIG_TEGRA186=y
 CONFIG_DEFAULT_DEVICE_TREE="tegra186-p2771-0000-500"
 CONFIG_OF_SYSTEM_SETUP=y
+CONFIG_CONSOLE_MUX=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="Tegra186 (P2771-0000-500) # "
 # CONFIG_CMD_IMI is not set