[flashrom] large file support

[Carl-Daniel Hailfinger]

I noticed that chipset_enable.c has #define _LARGEFILE64_SOURCE but it
does not perform any open/seek, whereas other files (especially
physmap.c) have no indication of large file support, yet they do use
open/seek.
Looking at the code history this seems to be an accident.

What's the correct way to get large file support, and do we need it at all?
Image files will probably stay smaller than 16 MB, so I see no real
problems there, but MSR support and physmap support may need this.

Regards,
Carl-Daniel