MAINTAINERS: Add myself for videotoolbox.c, remove vda* maintainer

Person in MAINTAINERS hasn't responded to a patch on the ML or private
email, and doesn't maintain the files according to git.

Signed-off-by: Rick Kern <kernrj@gmail.com>

MAINTAINERS

@@ -306,9 +306,8 @@ Hardware acceleration:
   mediacodec*                           Matthieu Bouron
   vaapi*                                Gwenole Beauchesne
   vaapi_encode*                         Mark Thompson
-  vda*                                  Sebastien Zwickert
   vdpau*                                Philip Langdale, Carl Eugen Hoyos
-  videotoolbox*                         Sebastien Zwickert
+  videotoolbox*                         Rick Kern
 
 
 libavdevice