HID: sony: Cache the output report for the Dualshock 4

Retrieve and cache the output report for the Dualshock 4 in sony_probe()
instead of repeatedly walking the report list in the worker function.

Signed-off-by: Frank Praznik <frank.praznik@oh.rr.com>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>