[coreboot-gerrit] Change in coreboot[master]: soc/mediatek: Add PCIe support

[Jianjun Wang (Code Review)]

Attention is currently required from: Shelley Chen, Hung-Te Lin, Furquan Shaikh, Paul Menzel, Yu-Ping Wu.
Jianjun Wang has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/56791 )

Change subject: soc/mediatek: Add PCIe support
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Patch Set 4:

(1 comment)

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

https://review.coreboot.org/c/coreboot/+/56791/comment/e124c385_898f275e 
PS2, Line 329: mtk_pcie_gen3_probe
> A lot of this code seems redundant as the common drivers in coreboot already provide support for: […]

Thanks for your suggestion, I removed most of these redundant functions, but there are still some resource allocation functions that I need to add in this code:
1. Use mtk_pcie_dev_assign_resource to maintain the usage of the MMIO space, in this platform, we have a 64MBytes MMIO space starting from 0x2000_0000;
2. Use mtk_pcie_bridge_assign_resources to update the resource base/size information of the bridge, let the config space of the root port can get the correct memory/io base/limit.