usb: dwc2: Rename dwc2_core_reset()

Renamed dwc2_core_reset() to dwc2_core_reset_and_force_dr_mode(). This
describes what it is doing more accurately. This is in preparation of
introducing a plain dwc2_core_reset() function that only performs the
reset and doesn't force the mode.

Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>