Added dwc2_gadget_program_ref_clk function to program GREFCLK
register in device mode.
Acked-by: NMinas Harutyunyan <hminas@synopsys.com>
Signed-off-by: NGrigor Tovmasyan <tovmasya@synopsys.com>
Signed-off-by: NFelipe Balbi <felipe.balbi@linux.intel.com>