ARM: dts: BCM5301X: Relicense Rafał's code to the GPL 2.0+ / MIT

All BCM5301X device DTS files use dual licensing. Try the same for SoC.
Introduce a new .dtsi file with a proper SPDX tag.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Link: https://lore.kernel.org/r/20230503121611.1629-1-zajec5@gmail.com


Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>