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/pine64_plus_defconfig b/configs/pine64_plus_defconfig
index 6f82190..348cbd4 100644
--- a/configs/pine64_plus_defconfig
+++ b/configs/pine64_plus_defconfig
@@ -6,6 +6,7 @@
 CONFIG_DRAM_ZQ=3881915
 CONFIG_DEFAULT_DEVICE_TREE="sun50i-a64-pine64-plus"
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
+CONFIG_CONSOLE_MUX=y
 # CONFIG_CMD_IMLS is not set
 # CONFIG_CMD_FLASH is not set
 # CONFIG_CMD_FPGA is not set