dwc3: Disable USB Link state(U1/U2) change events

Currently all USB Link state change events are enable which are
triggering huge number of interrupts to the cpu. Disable U1/U2 Link
state entry/exit events by using dwc_usb3_devten register. Below is
one of test results showing the same.
Test case: Run tethered RMNET UDP UL/DL Modem looback with 50M bandwidth
Test duration: 120 seconds
Test Results :
- with USB Link state change events enable:
CPU Idle : 42%, Number of USB Link state change events: 3769013
- with USB Link state change events disable:
CPU Idle : 51%, Number of USB Link state change events: 0
These numbers (cpu usage, number of interrupts) are taken for
120 seconds duration of test execution.

This change also does enable U3L2L1SuspEn event (BIT:6)  to get U3
notification and handling suspend part. Wakeup event is already enabled
which takes care of USB resuming.

CRs-Fixed: 610718
Change-Id: Ied6da6699849a3136a35de0b9a27ee18086daeab
Signed-off-by: Mayank Rana <mrana@codeaurora.org>