Revert "[media] dvb/audio.h: Remove definition for AUDIO_GET_PTS"

Based on those feedback:
	http://www.spinics.net/lists/linux-media/msg33704.html
	http://www.spinics.net/lists/linux-media/msg33700.html



I'm reverting the removal of this unused ioctl, as it seems that some
drivers under development may be using. So, I'll wait until the next
merge window before removing those unused ioctls, to give a chance for
developers to submit their pending work.

This reverts commit db48923da6c528d461b5e764692239eb9c1b7a00.

Cc: Andreas Oberritter <obi@linuxtv.org>
Cc: Manu Abraham <abraham.manu@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>