MAINTAINERS: update DT binding doc locations

After the recent moving of DT binding documents, some maintainers entries
are stale. Update them to the new locations.

In bindings/fb/, there were only 2 files and I'm assuming the FB
maintainers don't want to be copied on all of bindings/display/. So I've
dropped them.

Reported-by: Thierry Reding <thierry.reding@gmail.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Jianwei Wang <jianwei.wang.chn@gmail.com>
Cc: Alison Wang <alison.wang@freescale.com>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Mark Yao <mark.yao@rock-chips.com>
Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: Vincent Abriou <vincent.abriou@st.com>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Rob Herring <robh@kernel.org>