This function really should have been taking virDevicePCIAddress*
instead of the inefficient virDevicePCIAddress (results in copying two
entire structs onto the stack rather than just two pointers), and
returning a bool true/false (not matching is not necessarily a
"failure", as a -1 return would imply, and also using "if
(!virDevicePCIAddressEqual(x, y))" to mean "if x == y" is just a bit
counterintuitive).