qemu_domain_address: use virPCIDeviceAddressEqual() in conditionals

qemu_domain_address: use virPCIDeviceAddressEqual() in conditionals

A common operation in qemu_domain_address is comparing a
virPCIDeviceAddress and assigning domain, bus, slot and function
to a specific value. The former can be done with the existing
virPCIDeviceAddressEqual() helper, as long as we provide
a virPCIDeviceAddress to compare it to.

The later can be done by direct assignment of the now existing
virPCIDeviceAddress struct. The defined values of domain, bus,
slot and function will be assigned to info->addr.pci, the other
values are zeroed (which happens to be their default values too).
It's also worth noticing that all these assignments are being
conditioned by virDeviceInfoPCIAddressIsPresent() calls, thus it's
sensible to discard any non-zero values that might happen to exist
in @cont->info.addr, if we settled beforehand that @cont->info.addr
is not present or bogus.

Suggested-by: Erik Skultety <eskultet@redhat.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>