PCI: tegra194: Disable LTSSM after transition to Detect on surprise link down

PCI: tegra194: Disable LTSSM after transition to Detect on surprise link down

After the link reaches a Detect-related LTSSM state, disable LTSSM so it
does not keep toggling between Polling and Detect. Do this by polling for
the Detect state first, then clearing APPL_CTRL_LTSSM_EN in both
tegra_pcie_dw_pme_turnoff() and pex_ep_event_pex_rst_assert().

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: Jon Hunter <jonathanh@nvidia.com>
Link: https://patch.msgid.link/20260324190755.1094879-4-mmaddireddy@nvidia.com