[M] Change in coreboot[main]: soc/mediatek: Add mtk_pcie_deassert_perst for early PCIe reset

[Yidi Lin (Code Review)]

Attention is currently required from: Hung-Te Lin, Jianjun Wang, Yidi Lin.

Hello Hung-Te Lin, Jianjun Wang, Yu-Ping Wu, build bot (Jenkins),

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/84117?usp=email

to look at the new patch set (#4).

Change subject: soc/mediatek: Add mtk_pcie_deassert_perst for early PCIe reset
......................................................................

soc/mediatek: Add mtk_pcie_deassert_perst for early PCIe reset

Even we assert PRSET# early to save the delay between PERST# assertion
and de-assertion. MediaTek PCIe driver still takes 47ms waiting for PCIe
link up. (1ms delay for each try)

```
[INFO ]  mtk_pcie_domain_enable: PCIe link up success (47 tries)
```

Refactor common/pcie.c and add mtk_pcie_deassert_perst for early PCIe
reset. So we can de-assert PERST# at early stage to improve the boot
time.

BUG=b:361728592
TEST=emerge-cherry coreboot

Change-Id: I008e95263bfaf0119353382c2d2ce5ce29c6a382
Signed-off-by: Yidi Lin 
---
M src/soc/mediatek/common/include/soc/pcie_common.h
M src/soc/mediatek/common/pcie.c
2 files changed, 54 insertions(+), 18 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/17/84117/4