arm: dts: armada-385-db-ap: use SPDX-License-Identifier
Follow the recent trend for the license description, and also fix the
wrongly stated X11 to MIT.
As already pointed on the DT ML, the X11 license text [1] is explicitly
for the X Consortium and has a couple of extra clauses. The MIT
license text [2] is actually what the current DT files claim.
Cc: Maxime Ripard <maxime.ripard@bootlin.com> Acked-by: Maxime Ripard <maxime.ripard@bootlin.com> Acked-by: Jason Cooper <jason@lakedaemon.net> Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>