MAINTAINERS: Add Archit as drm bridge maintainer

Again something that's in the drm-misc fold.

Cc: Archit Taneja <architt@codeaurora.org>
Acked-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161116140819.31165-3-daniel.vetter@ffwll.ch