intel/skylake: Fix UART build options

1. skylake does not support UART over I/O. So, NO_UART_ON_SUPERIO needs
to be selected by default.
2. Move BOOTBLOCK_CONSOLE under UART_DEBUG.
3. Include bootblock/uart.c only if UART_DEBUG is selected.

Change-Id: I4e996bea2a25b3b1dfb9625d97985a9d3473561b
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/16025
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)

src/soc/intel/skylake/Kconfig

@@ -13,7 +13,6 @@ config CPU_SPECIFIC_OPTIONS
 	select ARCH_ROMSTAGE_X86_32
 	select ARCH_VERSTAGE_X86_32
 	select ACPI_NHLT
-	select BOOTBLOCK_CONSOLE
 	select CACHE_MRC_SETTINGS
 	select CACHE_RELOCATED_RAMSTAGE_OUTSIDE_CBMEM if RELOCATABLE_RAMSTAGE
 	select C_ENVIRONMENT_BOOTBLOCK
@@ -159,9 +158,11 @@ config VGA_BIOS_ID
 config UART_DEBUG
 	bool "Enable UART debug port."
 	default n
+	select BOOTBLOCK_CONSOLE
 	select CONSOLE_SERIAL
 	select DRIVERS_UART
 	select DRIVERS_UART_8250MEM_32
+	select NO_UART_ON_SUPERIO
 
 config CHIPSET_BOOTBLOCK_INCLUDE
 	string

src/soc/intel/skylake/Makefile.inc

@@ -14,7 +14,7 @@ bootblock-y += bootblock/cache_as_ram.S
 bootblock-y += bootblock/cpu.c
 bootblock-y += bootblock/pch.c
 bootblock-y += bootblock/systemagent.c
-bootblock-y += bootblock/uart.c
+bootblock-$(CONFIG_UART_DEBUG) += bootblock/uart.c
 bootblock-y += gpio.c
 bootblock-y += monotonic_timer.c
 bootblock-y += pch.c