media: v4l2-mem2mem.h: fix typo in comment

The comment describing the function v4l2_m2m_last_src_buf() says that this
function returns the last destination buffer when it actually returns the
last source buffer. Fix the comment so that it is accurate.

Signed-off-by: Deborah Brouwer <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

include/media/v4l2-mem2mem.h

···
 struct vb2_v4l2_buffer *v4l2_m2m_last_buf(struct v4l2_m2m_queue_ctx *q_ctx);
 
 /**
- * v4l2_m2m_last_src_buf() - return last destination buffer from the list of
+ * v4l2_m2m_last_src_buf() - return last source buffer from the list of
  * ready buffers
  *
  * @m2m_ctx: m2m context assigned to the instance given by struct &v4l2_m2m_ctx