xhci: fix debugfs register accesses while suspended

xhci: fix debugfs register accesses while suspended

commit 735baf1b23458f71a8b15cb924af22c9ff9cd125 upstream.

Wire up the debugfs regset device pointer so that the controller is
resumed before accessing registers to avoid crashing or locking up if it
happens to be runtime suspended.

Fixes: 2100b998f426 ("usb: xhci: Add debugfs interface for xHCI driver")
Cc: stable@vger.kernel.org # 4.15: 94bd87e85813: debugfs: regset32: Add Runtime PM support
Cc: stable@vger.kernel.org # 4.15
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20230405090342.7363-1-johan+linaro@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>