usb: dwc3: update LC timer as per new usb V3.20

This is the workaround for STAR 9001285599 which affects
dwc3 core version 3.20a only. The timer value for PM_LC_TIMER
in V3.20a for the Link ECN changes is not correct. If the PM TIMER
ECN is enabled thru GUCTL2[19], then link compliance test (TD7.21)
may fail. If the ECN is not enabled (GUCTL2[19] = 0), the controller
will use the old timer value (5us), which is still fine for Link
Compliance test. Hence Clear GUCTL2[19] to pass usb link compliance
test: TD 7.21.

Change-Id: I5fc535ef2bdd54764086a50cf9a3cb538f92a465
Signed-off-by: Chandana Kishori Chiluveru <cchiluve@codeaurora.org>