intel_bios_dumper: handle rom_size == 0
intel_bios_dumper: handle rom_size == 0

Some versions of libpciaccess on Linux set rom_size to 0 for VGA
devices.  While this behavior may change, intel_bios_dumper should
handle this situation to be compatible with current versions of the
library.

This fixes segmentation faults on affected systems.

Signed-off-by: Forest Bond <7350bf649febf6696b1fdeae3c0f18bcb6ce69e7@rapidrollout.com>
Signed-off-by: Chris Wilson <711c73f64afdce07b7e38039a96d2224209e9a6c@chris-wilson.co.uk>

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