Existing test cases determine secureboot state using efi variable, which is available only on x86 architecture. Add support for determining secureboot state using device tree property on PowerNV architecture. Signed-off-by: Nageswara R Sastry <rnsastry@linux.ibm.com> Reviewed-by: Nayna Jain <nayna@linux.ibm.com> Tested-by: Nayna Jain <nayna@linux.ibm.com> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>