V4L/DVB (3375): Add AUDIO_GET_PTS and VIDEO_GET_PTS ioctls

Add two new ioctls to read the 33 bit presentation time stamp from audio
and video devices as defined in ITU T-REC-H.222.0 and ISO/IEC 13818-1.
Acked-by: Johannes Stezenbach <js@linuxtv.org>

Signed-off-by: Andreas Oberritter <obi@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>