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/B4420QDS_NAND_defconfig b/configs/B4420QDS_NAND_defconfig
index c192177..d3cf286 100644
--- a/configs/B4420QDS_NAND_defconfig
+++ b/configs/B4420QDS_NAND_defconfig
@@ -14,6 +14,7 @@
 CONFIG_OF_STDOUT_VIA_ALIAS=y
 CONFIG_SYS_EXTRA_OPTIONS="PPC_B4420,RAMBOOT_PBL,SPL_FSL_PBL,NAND"
 CONFIG_BOOTDELAY=10
+CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 CONFIG_SPL=y
 CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT=y
 CONFIG_HUSH_PARSER=y