usb: dwc3: pci: Set enblslpm quirk for Synopsys platforms

Certain Synopsys prototyping PHY boards are not able to meet timings
constraints for LPM. This allows the PHY to meet those timings by
leaving the PHY clock running during suspend.

Cc: <stable@vger.kernel.org> # v3.18+
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>