dwc: pcie-qcom-ep: Add QCOM PCIe endpoint driver

Add PCIe end point controller which uses the Synopsis Designware
core and additional wrapper around the core. The End point
supports ASPM and PM states. The driver supports capability
to wake up the host using side band GPIO WAKE# in D3_COLD
or inband PME wake when device is in D3_HOT state.

Use the DW framework to register the controller and use existing
functions for access to config space using DBI. Register the
end point device with DW endpoint framework to utilize functions
to configure the config space.

Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>