drivers/pc80/Kconfig: Mention that GRUB 2 is able to init PS/2 keyboard

Change-Id: I0783ee123e0e1ecd5603bc6a40b53d3b0c23bf6d
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-on: http://review.coreboot.org/5582
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
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>
drivers/pc80/Kconfig: Do not init PS/2 keyboard if GRUB 2 is chosen as payload

If the user selects GRUB 2 as the payload in Kconfig, coreboot does
not need to initialize the PS/2 keyboard as GRUB 2 is going to do it.

Change-Id: Ia5d902e7c0fa34eaff26a31507751815bf2d2581
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-on: http://review.coreboot.org/5583
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>