MAINTAINERS: add myself to OMX

Signed-off-by: Aman Gupta <aman@tmm1.net>
Signed-off-by: Martin Storsjö <martin@martin.st>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

MAINTAINERS

@@ -213,6 +213,7 @@ Codecs:
   msvideo1.c                            Mike Melanson
   nuv.c                                 Reimar Doeffinger
   nvdec*, nvenc*                        Timo Rothenpieler
+  omx.c                                 Martin Storsjo, Aman Gupta
   opus*                                 Rostislav Pehlivanov
   paf.*                                 Paul B Mahol
   pcx.c                                 Ivo van Poorten