When QEMU provides the equivalent of the EL3 firmware, we
need to enable HVCs in scr_el3 when turning on CPUs that
target EL2.
Backports commit 86278c33d1d71196f5e22ce3ce82a1b34a199754 from qemu
Split ARM on/off function from PSCI support code.
This will allow to reuse these functions in other code.
Backports commit 825482adde1f971cbddf27e15fb4453ab3fae994 from qemu