[LinuxBIOS] Make testbios understand PCI bus:dev.func

[Richard Smith]

The following patch makes testbios understand what to do with a device
that is specified as bus:dev.func or dev.func.  If you just give it
one number then its works like the original.

so '-d 0:9.0' or '-d 9.0' will translate to devfn of 0x48

It also add a sanity check for the device if you appear to be running
an option ROM.  So if you fail to specify a device or your -d
parameter works out to 0 it prints a warning message.