usb: dwc3: Add support for setting LPM_NYET_THRESH

Add support to set the LPM_NYET_THRESH parameter.
If BESL value received from the host in the LPM token is
less than this value we send LPM ACK to the host.
Otherwise the device returns LPM NYET

Change-Id: I360c89c5a7d927ad1fc16a4994cdbdf8a5120d5a
Signed-off-by: Mayank Rana <mrana@codeaurora.org>