[S] Change in flashrom[main]: Provide an option to use PCI_ACCESS_ECAM to access pci register

[Kane Chen (Code Review)]

Attention is currently required from: Hsuan Ting Chen, Hsuan-ting Chen, Kane Chen, Peter Marheine.

Kane Chen has posted comments on this change by Kane Chen. ( https://review.coreboot.org/c/flashrom/+/83896?usp=email )

Change subject: Provide an option to use PCI_ACCESS_ECAM to access pci register
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Patch Set 3:

(1 comment)

File meson_options.txt:

https://review.coreboot.org/c/flashrom/+/83896/comment/d341e2b2_0241c83c?usp... :
PS3, Line 9: option('use_libpci_ecam', type : 'boolean', value : false)
> It looks like this is only used for 100-series PCHs which presumably always support ECAM, so is this […]

My original thought is to avoid any potential impact since i only have chromebooks to verify. 
if it's ok to use ECAM directly, i can remove this option.
thank you