[media] v4l2-mem2mem: clear m2m queue ready counter in v4l2_m2m_streamoff

v4l2_m2m_streamoff drops the list of ready buffers but failed to reset the
num_rdy counter to zero. This would lead to v4l2_m2m_num_src/dst_bufs_ready
reporting wrong values after streamoff.

Signed-off-by: Philipp Zabel <[e-mail]>
Signed-off-by: Kamil Debski <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/v4l2-core/v4l2-mem2mem.c

···
 	/* Drop queue, since streamoff returns device to the same state as after
 	 * calling reqbufs. */
 	INIT_LIST_HEAD(&q_ctx->rdy_queue);
+	q_ctx->num_rdy = 0;
 	spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);
 
 	if (m2m_dev->curr_ctx == m2m_ctx) {