[IrDA] af_irda: irda_recvmsg_stream cleanup

This patch cleans up some code in irda_recvmsg_stream, replacing some
homebrew code with prepare_to_wait/finish_wait, and by making the
code honor sock_rcvtimeo.

Signed-off-by: Olaf Kirch <olaf.kirch@oracle.com>
Signed-off-by: Samuel Ortiz <samuel@sortiz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>