linuxkpi: Add `pci_map_rom()` and `pci_unmap_rom()`

[dumbbell]

Summary

They were already defined as macros in various places in DRM drivers, aliasing the vga_pci_map_bios() and vga_pci_unmap_bios() functions. Let's move them to linuxkpi and avoid copies everywhere.

Because they use the vga_pci code internally, pci_map_rom() checks whether the given device is a video card. If it is not, it logs a "TODO" and returns NULL.