hidraw: Return EPOLLOUT from hidraw_poll

Always return EPOLLOUT from hidraw_poll when a device is connected.
This is safe since writes are always possible (but will always block).

hidraw does not support non-blocking writes and instead always calls
blocking backend functions on write requests. Hence, so far, a call to
poll never returned EPOLLOUT, which confuses tools like socat.
Signed-off-by: NFabian Henneke <fabian.henneke@gmail.com>
In-reply-to: <CA+hv5qkyis03CgYTWeWX9cr0my-d2Oe+aZo+mjmWRXgjrGqyrw@mail.gmail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

drivers/hid/hidraw.c

@@ -252,7 +252,7 @@ static __poll_t hidraw_poll(struct file *file, poll_table *wait)
 
 	poll_wait(file, &list->hidraw->wait, wait);
 	if (list->head != list->tail)
-		return EPOLLIN | EPOLLRDNORM;
+		return EPOLLIN | EPOLLRDNORM | EPOLLOUT;
 	if (!list->hidraw->exist)
 		return EPOLLERR | EPOLLHUP;
 	return 0;