usb: dwc3: gadget: Rename misleading function names

The functions dwc3_prepare_one_trb_sg and dwc3_prepare_one_trb_linear
are not necessarily preparing "one" TRB, it can prepare multiple TRBs.
Rename these functions as follow:

dwc3_prepare_one_trb_sg -> dwc3_prepare_trbs_sg
dwc3_prepare_one_trb_linear -> dwc3_prepare_trbs_linear

Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>