usb: dwc3: Add trace event for dwc3_set_prtcap

usb: dwc3: Add trace event for dwc3_set_prtcap

Changes to the port capability can be indirectly observed by tracing
register writes to DWC3_GCTL. However, this requires interpreting the
raw value, which is neither intuitive nor precise for debugging.
Monitoring these mode changes is essential for resolving issues related
to USB role switching and enumeration.

Introduce a dedicated trace event to provide a human-readable log when
the port capability is configured.

Signed-off-by: Kuen-Han Tsai <khtsai@google.com>
Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/20250822092411.173519-1-khtsai@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>