DocBook/drm: Use the passive voice

	using the pci_map_rom() call, a convenience function that

	takes care of mapping the actual ROM, whether it has been

	shadowed into memory (typically at address 0xc0000) or exists

	on the PCI device in the ROM BAR.  Note that once you've

	mapped the ROM and extracted any necessary information, be

	sure to unmap it; on many devices the ROM address decoder is

	on the PCI device in the ROM BAR.  Note that after the ROM

	has been mapped and any necessary information has been extracted,

	it should be unmapped; on many devices the ROM address decoder is

	shared with other BARs, so leaving it mapped can cause

	undesired behavior like hangs or memory corruption.

<!--!Fdrivers/pci/rom.c pci_map_rom-->