usb: gadget: Export recommended BESL values

Currently there's no option for the controller driver to report the
recommended Best Effort Service Latency (BESL) when operating with LPM
support. Add new fields in usb_dcd_config_params to export the
recommended baseline and deep BESL values for the function drivers to
set the proper BESL value in the BOS descriptor.

Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>