mm-core: Add MPEG-2 extension and user data types

With this commit, OMX_ExtraDataMP2ExtnData and
OMX_ExtraDataMP2UserData eTypes are added to support
MPEG-2 extra data types.

Change-Id: Iffd6e216d9f6fdf30f6a99410c353a37bbe14dc7

Conflicts:
	mm-core/inc/OMX_QCOMExtns.h