x86: baytrail: Introduce a Kconfig option for the internal UART

There are quite a number of BayTrail boards that uses an external
SuperIO chipset to provide the legacy UART. For such cases, it's
better to have a Kconfig option to enable the internal UART.

So far BayleyBay and MinnowMax boards are using internal UART as
the U-Boot console, enable this on these two boards.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/x86/cpu/baytrail/Kconfig

@@ -7,3 +7,14 @@
 config INTEL_BAYTRAIL
 	bool
 	select HAVE_FSP if !EFI
+
+if INTEL_BAYTRAIL
+config INTERNAL_UART
+	bool "Enable the SoC integrated legacy UART"
+	help
+	  There is a legacy UART integrated into the Bay Trail SoC.
+	  A maximum baud rate of 115200 bps is supported. For this
+	  reason, it is recommended that the UART port be used for
+	  debug purposes only, eg: U-Boot console.
+
+endif

configs/bayleybay_defconfig

@@ -2,6 +2,7 @@ CONFIG_X86=y
 CONFIG_VENDOR_INTEL=y
 CONFIG_DEFAULT_DEVICE_TREE="bayleybay"
 CONFIG_TARGET_BAYLEYBAY=y
+CONFIG_INTERNAL_UART=y
 CONFIG_HAVE_INTEL_ME=y
 CONFIG_ENABLE_MRC_CACHE=y
 CONFIG_SMP=y

configs/minnowmax_defconfig

@@ -2,6 +2,7 @@ CONFIG_X86=y
 CONFIG_VENDOR_INTEL=y
 CONFIG_DEFAULT_DEVICE_TREE="minnowmax"
 CONFIG_TARGET_MINNOWMAX=y
+CONFIG_INTERNAL_UART=y
 CONFIG_HAVE_INTEL_ME=y
 CONFIG_ENABLE_MRC_CACHE=y
 CONFIG_SMP=y