HID: hidraw: close underlying device at removal of last reader

Even though device exist bit is set the underlying
HW device should be closed when the last reader
of the device is closed i.e. open count drops to zero.

Signed-off-by: Manoj Chourasia <mchourasia@nvidia.com>
Reported-by:  <mika.westerberg@linux.intel.com>
Tested-by:  <mika.westerberg@linux.intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>