stagefright: Enable 24-bit mode for DTS audio

 * FFMPEG will convert floating point samples to 24-bit PCM
   if the system is capable of it.

Change-Id: I14fb015468166e567a17bf8758474788e1c285e9

Conflicts:
	media/libstagefright/ExtendedUtils.cpp
	media/libstagefright/include/ExtendedUtils.h