Replace the shared lib dependency to libmedia with header deps

libstagefright_mpeg2support actually doesn't link with libmedia. It uses
headers from the library. Replace the shared lib dependency to the
library with the header lib dependency to libmedia_headers and
libaudioclient_headers.

Bug: N/A
Test: m libstagefright_mpeg2support
Change-Id: I87dba95b344eb95c9d36746c8234640815236956