SeaBIOS: Disable serial console if serial is memory mapped

SeaBIOS only supports standard IO based serial ports.  If the serial
port being used by coreboot isn't a standard IO serial port, disable
the serial console in the SeaBIOS build.

Change-Id: I386b46625fca0bd0a5416ed9831f8370c294ed74
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/13617
Tested-by: build bot (Jenkins)
Reviewed-by: Leroy P Leahy <leroy.p.leahy@intel.com>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

payloads/external/SeaBIOS/Makefile.inc

@@ -25,7 +25,7 @@ checkout: fetch
 config: checkout
 	echo "    CONFIG     SeaBIOS $(TAG-y)"
 	echo "CONFIG_COREBOOT=y" > seabios/.config
-ifeq ($(CONFIG_CONSOLE_SERIAL),y)
+ifeq ($(CONFIG_CONSOLE_SERIAL)$(CONFIG_DRIVERS_UART_8250IO),yy)
 	echo "CONFIG_DEBUG_SERIAL=y" >> seabios/.config
 	echo "CONFIG_DEBUG_SERIAL_PORT=$(CONFIG_TTYS0_BASE)" >> seabios/.config
 else