[SeaBIOS] [PATCH] Add option to only execute CBFS option ROMs

[Timothy Pearson]

All,

This is my first time submitting a patch to SeaBIOS for 
review/inclusion; I assume this list is the correct initial contact?

I have run into several situations where it is neccessary to execute 
only the relevant option ROMs contained in CBFS while ignoring any 
option ROM binary code present on PCI/PCIe devices; e.g. when the option 
ROM provided by the manufacturer is buggy but a FOSS replacement is 
available that works properly.

This patch adds an option to only execute option ROMs contained in CBFS. 
  Tested on ASUS KFSN4-DRE with iPXE ROMs built in to CBFS; with this 
option set the on-board network ROMs were ignored while the iPXE ROMs 
executed normally.