HID: usbhid: do not rely on hid->open when deciding to do IO

Instead of checking hid->open (that we plan on having HID core manage) in
hid_start_in(), let's allocate a couple of new flags: HID_IN_POLLING and
HID_OPENED, and use them to decide whether we should be submitting URBs or
not.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>