arm64: dts: verdin-imx8mm: verdin-imx8mp: improve include notation

Improve include notation. Usually only dtsi files from the same location
are included with an absolute path in quotes. Others should use a
relative path enclosed in angle brackets.

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>