powerpc/rtas: avoid device tree lookups in rtasosterm()
This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v5.10.163 by commit f2167f10fcca68ab9ae3f8d94d2c704c5541ac69. For more details please see the references link.