MAINTAINERS: update designated reviewer entry for MSM DRM driver

Adding myself as a designated reviewer to assist with the
code reviews for the changes coming into MSM DRM.
Acked-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Link: https://lore.kernel.org/r/1637394371-16783-1-git-send-email-quic_abhinavk@quicinc.comSigned-off-by: Rob Clark <robdclark@chromium.org>

MAINTAINERS

@@ -6038,6 +6038,7 @@ F:	drivers/gpu/drm/tiny/mi0283qt.c
 DRM DRIVER FOR MSM ADRENO GPU
 M:	Rob Clark <robdclark@gmail.com>
 M:	Sean Paul <sean@poorly.run>
+R:	Abhinav Kumar <quic_abhinavk@quicinc.com>
 L:	linux-arm-msm@vger.kernel.org
 L:	dri-devel@lists.freedesktop.org
 L:	freedreno@lists.freedesktop.org