soc/intel/cannonlake: Add Kconfig option to select UART index

Cannonlake SOC has two possible ways to make serial
console functional.

1. Legacy IO based access using Port 0x3F8.
2. LPSS UART PCI based access.

This patch to provide option to select index for LPSS
UART port: 0 = LPSS UART0, 1 = LPSS UART1, 2 = LPSS UART2

PCI based LPSS UART2 is by default enabled for Chrome Design.

Change-Id: I7afa5ab2c5eb06e6df8eeb1cb1cd0de00d2b2a28
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-on: https://review.coreboot.org/20998
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/cannonlake/Kconfig

@@ -56,6 +56,13 @@ config UART_DEBUG
 	select DRIVERS_UART
 	select DRIVERS_UART_8250IO
 
+config UART_FOR_CONSOLE
+	int "Index for LPSS UART port to use for console"
+	default 2 if DRIVERS_UART_8250MEM
+	help
+	    Index for LPSS UART port to use for console:
+	    0 = LPSS UART0, 1 = LPSS UART1, 2 = LPSS UART2
+
 config DCACHE_RAM_BASE
 	default 0xfef00000