libstagefright: Add Dolby UDC decoder support

Add support for ARM based AC3/EAC3 decoder

Change-Id: I63e994fca23479ea9f7c68d5f008eed00cbafffd
libstagefright: Additional UDC software decoder support
patches

This is principally to allow merging into CAF. AC3/EC3
mime-type definitions removed to prevent duplication.

Change-Id: I09847a09b0f0780798a82cff7b31b2207c267769