HID: logitech: check the return value of create_singlethread_workqueue

create_singlethread_workqueue may fail and return NULL. The fix checks if it is
NULL to avoid NULL pointer dereference.  Also, the fix moves the call of
create_singlethread_workqueue earlier to avoid resource-release issues.

Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>