MAINTAINERS: add myself as rtpdec_mpa_robust maintainer

Signed-off-by: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

MAINTAINERS

@@ -471,6 +471,7 @@ Muxers/Demuxers:
   rtpdec_dv.*                           Thomas Volkert
   rtpdec_h261.*, rtpenc_h261.*          Thomas Volkert
   rtpdec_hevc.*, rtpenc_hevc.*          Thomas Volkert
+  rtpdec_mpa_robust.*                   Gilles Chanteperdrix
   rtpdec_asf.*                          Ronald S. Bultje
   rtpdec_vp9.c                          Thomas Volkert
   rtpenc_mpv.*, rtpenc_aac.*            Martin Storsjo