Allow Powerdown menu for devices other than M1

Just because device can't power itself off, doesn't mean system shouldn't be given opportuntity to have a clean exit from xbmc.

This renables Powerdown menu so S95-xbmc script has a chance to run and dismount drives and removable media.

On M3 users will have to physically remove power to power off.
[aml] changed, track width, height and frame rate as well as aspect ration for mpeg2 video content
[aml] changed, kernel driver contains default 'decoder ppmgr amvideo' vfm map so we do not need to diddle these anymore
Merge pull request #7 from toys4me/PR/SafeShutdown

Allow Powerdown menu for devices other than M1
[aml] fixed, track speed even if decoder is not open
changed, assert(0) is nasty, this could just be a bad audio packet