MAINTAINERS: of: collapse overlay entry into main device tree entry

Pantelis has not been active in recent years so no need to maintain
a separate entry for device tree overlays.

Signed-off-by: Frank Rowand <frank.rowand@sony.com>
Link: https://lore.kernel.org/r/20221012220548.4163865-1-frowand.list@gmail.com


Signed-off-by: Rob Herring <robh@kernel.org>