usb: dwc3: st: Inform the reset framework that our reset line may be shared

On the STiH410 B2120 development board the MiPHY28lp shares its reset
line with the Synopsys DWC3 SuperSpeed (SS) USB 3.0 Dual-Role-Device
(DRD).  New functionality in the reset subsystems forces consumers to
be explicit when requesting shared/exclusive reset lines.

Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>