FROMLIST: PCI: mediatek-gen3: Keep PCIe power and clocks if suspend-to-idle

If the target system sleep state is suspend-to-idle, the bridge is
supposed to stay in D0, and the framework will not help to restore its
configuration space, so keep its power and clocks during suspend.

It's recommended to enable L1ss support, so the link can be changed to
L1.2 state during suspend.

Signed-off-by: Jianjun Wang <jianjun.wang@mediatek.com>
(am from https://patchwork.kernel.org/patch/13925179/)
(also found at https://lore.kernel.org/r/20250103060035.30688-6-jianjun.wang@mediatek.com

)

BUG=b:383258443
TEST=build pass and boot to shell
UPSTREAM-TASK=b:379039276

Change-Id: Iedb16bdb94509f3ff9add564f959695d78ba3303
Signed-off-by: Hsin-Te Yuan <yuanhsinte@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/6174701


Tested-by: Fei Shao <fshao@chromium.org>
Reviewed-by: Fei Shao <fshao@chromium.org>
Reviewed-by: Sean Paul <sean@poorly.run>
Commit-Queue: Fei Shao <fshao@chromium.org>
Signed-off-by: Hubert Mazur <hmazur@google.com>