MTP: Fix partial implementation of 5 new audio specific properties

In change Ic5b3fb75309893caae1a4f4b56068a543847f1f7, we added partial
support for the MTP properties:

MTP_PROPERTY_AUDIO_WAVE_CODE,
MTP_PROPERTY_BITRATE_TYPE
MTP_PROPERTY_AUDIO_BITRATE
MTP_PROPERTY_NUMBER_OF_CHANNELS
MTP_PROPERTY_SAMPLE_RATE

However we were not returning any values for these properties in the result
of the MTP GetObjectPropList command. Strangely, this triggers a nasty bug
in Windows 7 that results in data loss.  When copying a directory containing
several MP3 files from one location on the device to another, Windows will
copy only some of the files to the new location, but delete all of the originals.
Finishing the implementation of these new object properties for some unknown
reason stops this bad behavior in Windows 7.

Bug: 19018427
Change-Id: I5fd3b91a89b31827d3100686445cef6795fe0f3f