[Makefile] Use bin/VVVVDDDD.rom instead of bin/pci_VVVV_DDDD.rom

The generate-by-PCI-device-ID rules (bin/pci_VVVV_DDDD.rom) are generally
used for building actual ROM images to be burned, and the burning
utilities generally run under some DOS variant.  Change the filename from
pci_VVVV_DDDD.rom to VVVVDDDD.rom so that it is compatible with the DOS
8.3-character filename limit.

src/util/parserom.pl

        \)/x ) {
     ( my $vendor, my $device, my $image, my $desc ) = ( lc $1, lc $2, $3, $4 );
     rom ( "pci", $image, $desc, $vendor, $device );
-    rom ( "pci", lc "pci_${vendor}_${device}", $desc, $vendor, $device );
+    rom ( "pci", lc "${vendor}${device}", $desc, $vendor, $device );
   } elsif ( /^\s*ISA_ROM\s*\(
 	      \s*\"([^\"]*)\"\s*,  # Image
 	      \s*\"([^\"]*)\"\s*   # Description