drivers/pc80/Kconfig: Do not init PS/2 keyboard if SeaBIOS is chosen as payload

As the Kconfig description of `DRIVERS_PS2_KEYBOARD` says, SeaBIOS is
able to initialize the PS/2 keyboard itself, so it is not necessary to
let coreboot do it.

SeaBIOS is also able to do it faster as discussed in a thread on the
coreboot mailing list from October 2010 [1]. In that thread it was
also proposed to not let coreboot initialize the PS/2 coreboot when
SeaBIOS is used as a payload.

[1] http://www.coreboot.org/pipermail/coreboot/2010-October/thread.html#61310
    subject: [coreboot] coreboot+seabios timings

Change-Id: I1248cec3e2ca5b9311e46df8aabf67e14ffd4ea6
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-on: http://review.coreboot.org/5581
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>

src/drivers/pc80/Kconfig

@@ -2,7 +2,8 @@
 # reliably support PS/2 init themselves.
 config DRIVERS_PS2_KEYBOARD
 	bool "PS/2 keyboard init"
-	default y
+	default n if PAYLOAD_SEABIOS
+	default y if !PAYLOAD_SEABIOS
 	help
 	  Enable this option to initialize PS/2 keyboards found connected
 	  to the PS/2 port.