arm64: dts: imx8ulp: no executable source file permission

This fixes the following error:

arch/arm64/boot/dts/freescale/imx8ulp-pinfunc.h: error: do not set
 execute permissions for source files

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Acked-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>