mainboard: use SeaBIOS config only when it's the payload of choice

It makes no sense for Das U-Boot which uses the same setting.

Change-Id: I1629aecf33cb62bb1e6856ef5627748a7dc74d8a
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Reviewed-on: https://review.coreboot.org/21611
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Martin Roth <martinroth@google.com>

src/mainboard/adi/rcc-dff/Kconfig

@@ -71,6 +71,7 @@ config UART_FOR_CONSOLE
 
 config PAYLOAD_CONFIGFILE
 	string
+	depends on PAYLOAD_SEABIOS
 	default "$(top)/src/mainboard/$(MAINBOARDDIR)/config_seabios"
 	help
 	  The Avoton/Rangeley chip does not allow devices to write into the 0xe000

src/mainboard/intel/littleplains/Kconfig

@@ -58,6 +58,7 @@ config UART_FOR_CONSOLE
 
 config PAYLOAD_CONFIGFILE
 	string
+	depends on PAYLOAD_SEABIOS
 	default "$(top)/src/mainboard/$(MAINBOARDDIR)/config_seabios"
 	help
 	  The Avoton/Rangeley chip does not allow devices to write into the 0xe000

src/mainboard/intel/mohonpeak/Kconfig

@@ -71,6 +71,7 @@ config UART_FOR_CONSOLE
 
 config PAYLOAD_CONFIGFILE
 	string
+	depends on PAYLOAD_SEABIOS
 	default "$(top)/src/mainboard/$(MAINBOARDDIR)/config_seabios"
 	help
 	  The Avoton/Rangeley chip does not allow devices to write into the 0xe000