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

[Yu-Ping Wu (Code Review)]

Attention is currently required from: Jianjun Wang.
Yu-Ping Wu 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 21:

(1 comment)

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

https://review.coreboot.org/c/coreboot/+/56791/comment/947c5e28_6b62ed9d 
PS21, Line 248: 	dev->chip_info = &pcie_ctrl;
Also, I don't think we should set chip_info in the code. It should be set in devicetree.cb instead. For example see

- mainboard/google/octopus/variants/baseboard/devicetree.cb
- soc_intel_apollolake_config in soc/intel/apollolake/chip.h

As a result, 'base', 'mmio_res_io' and 'mmio_res_mem' in mtk_pcie_controller should be defined in devicetree. As for ctrl->reset, we can call mtk_pcie_reset() directly (need to add it to a header file so that each SoC can implement its own version).