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/B4860QDS_SECURE_BOOT_defconfig b/configs/B4860QDS_SECURE_BOOT_defconfig
index 75124a8..2923547 100644
--- a/configs/B4860QDS_SECURE_BOOT_defconfig
+++ b/configs/B4860QDS_SECURE_BOOT_defconfig
@@ -8,6 +8,7 @@
 CONFIG_OF_STDOUT_VIA_ALIAS=y
 CONFIG_SYS_EXTRA_OPTIONS="PPC_B4860,SECURE_BOOT"
 CONFIG_BOOTDELAY=10
+CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_GREPENV=y
 CONFIG_CMD_SF=y