usb: roles: fix NULL pointer issue when put module's reference

usb: roles: fix NULL pointer issue when put module's reference

In current design, usb role class driver will get usb_role_switch parent's
module reference after the user get usb_role_switch device and put the
reference after the user put the usb_role_switch device. However, the
parent device of usb_role_switch may be removed before the user put the
usb_role_switch. If so, then, NULL pointer issue will be met when the user
put the parent module's reference.

This will save the module pointer in structure of usb_role_switch. Then,
we don't need to find module by iterating long relations.

Fixes: 5c54fcac9a9d ("usb: roles: Take care of driver module reference counting")
cc: stable@vger.kernel.org
Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20240129093739.2371530-1-xu.yang_2@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>