kvm tools: Fix up PCI pin assignment to conform specification

Only 4 pins are allowed for every PCI compilant device as per PCI 2.2 spec
Section 2.2.6 ("Interrupt Pins"). Multifunctional devices can use up to all
INTA#,B#,C#,D# pins, for our single function devices pin INTA# is enough.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>