PCI: tegra194: Don't force the device into the D0 state before L2

PCI: tegra194: Don't force the device into the D0 state before L2

As per PCIe CEM r6.0, sec 2.3, the PCIe Endpoint device should be in D3cold
to assert WAKE# pin. The previous workaround that forced downstream devices
to D0 before taking the link to L2 cited PCIe r4.0, sec 5.2, "Link State
Power Management"; however, that spec does not explicitly require putting
the device into D0 and only indicates that power removal may be initiated
without transitioning to D3hot.

Remove the D0 workaround so that Endpoint devices can use wake
functionality (WAKE# from D3). With some Endpoints the link may not enter
L2 when they remain in D3, but the Root Port continues with the usual flow
after PME timeout, so there is no functional issue.

Fixes: 56e15a238d92 ("PCI: tegra: Add Tegra194 PCIe support")
Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-by: Vidya Sagar <vidyas@nvidia.com>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Link: https://patch.msgid.link/20260324190755.1094879-5-mmaddireddy@nvidia.com