staging: dwc2: change some dev_dbg() messages to dev_vdbg()

Change some dev_dbg() messages in dwc2_hcd_hub_control() to
dev_vdbg(), to prevent massive spew to the dmesg log when a device
is disconnected.

Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>