MAINTAINERS: Add T.J. Mercier as reviewer for DMA-BUF HEAPS FRAMEWORK

T.J. has been responsible for dmab-buf items on the Android team
for awhile now, so it would be great to have him on as a reviewer.

Cc: T.J. Mercier <tjmercier@google.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Cc: Brian Starkey <Brian.Starkey@arm.com>
Cc: John Stultz <jstultz@google.com>
Cc: linux-media@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: kernel-team@android.com
Signed-off-by: John Stultz <jstultz@google.com>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230630045246.1674919-1-jstultz@google.com