aries-common: update media_codecs.xml for 4.3

* Add GSM decoder explicity
* Add VPX encoder (now required for 4.3 compatibility)

Change-Id: I7e6e79254313edb9159a495749b8200b13c8af42
Signed-off-by: Pawit Pornkitprasan <p.pawit@gmail.com>