[flashrom] PCI BAR access thru sysfs

[Ed Swierk]

Various kernel options are known to interfere with flashrom's attempts to
access physical memory through /dev/mem. Some (like CONFIG_STRICT_DEVMEM)
are important security measures that cannot be disabled without recompiling
the kernel, and are likely to be used more widely over time.

However, complete access to physical memory is unnecessary for some use
cases. For example, the SPI interface on an Intel NIC can be accessed by
mmapping a BAR resource file in the PCI device directory in sysfs. Has
anyone considered implementing such an alternative access method for PCI
devices in flashrom?

--Ed