Provide a utility to quickly determine the ROM size and .mrom format
support for attached PCI devices.  For example:

    01:00.0 (1186:4300) supports a 128kB .rom or .mrom

Inspired-by: Wes Frazier <wes.frazier@members.fsf.org>
Signed-off-by: Michael Brown <mcb30@ipxe.org>