PCI: qcom: Program T_POWER_ON

PCI: qcom: Program T_POWER_ON

Some platforms have incorrect T_POWER_ON value programmed in hardware.
Generally these will be corrected by bootloaders, but not all targets
support bootloaders to program correct values. That means the
LTR_L1.2_THRESHOLD value calculated by aspm.c can be wrong, which can
result in improper L1.2 exit behavior. If AER happens to be supported and
enabled, the error may be *reported* via AER.

Parse the 't-power-on-us' property from each Root Port node and program it
as part of host initialization using dw_pcie_program_t_power_on() before
link training.

This property in added to the dtschema here [1].

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
[mani: reworded comment]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link[1]: https://lore.kernel.org/all/20260205093346.667898-1-krishna.chundru@oss.qualcomm.com/
Link: https://patch.msgid.link/20260428-t_power_on_fux-v5-3-f1ef926a91ff@oss.qualcomm.com