Change in coreboot[master]: soc/mediatek: Add chip config for setting PCIe controller data

[Jianjun Wang (Code Review)]

Attention is currently required from: Hung-Te Lin, Rex-BC Chen, Yu-Ping Wu.
Jianjun Wang has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/62791 )

Change subject: soc/mediatek: Add chip config for setting PCIe controller data
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Patch Set 2:

(1 comment)

File src/soc/mediatek/common/pcie.c:

https://review.coreboot.org/c/coreboot/+/62791/comment/cde6b6f1_ff6be185 
PS2, Line 109: pcie_ctrl
> This global variable makes me wonder if putting the 'base' in the devicetree is the right decision. […]

I think it's ok to use PCIE_REG_BASE.
Another way to get the base address is by "pcidev_path_on_root(pci_devfn devfn)", we can get the device first, and get the config data from config_of(dev), but it will take more time than just define it.