Change protected KVM kernel parameter

During code review the parameter was changed to a more generic
kvm-arm.mode=protected.

Change-Id: I0d9ff54a69626de372d213735000d0cafe2d2f3e
diff --git a/aarch64/run_qemu.sh b/aarch64/run_qemu.sh
index b18ca42..9ffea8c 100755
--- a/aarch64/run_qemu.sh
+++ b/aarch64/run_qemu.sh
@@ -186,7 +186,7 @@
 fi
 
 if [ "${KVM_PROTECTED}" -eq 1 ]; then
-	APPEND+=(kvm-arm.protected=1)
+	APPEND+=(kvm-arm.mode=protected)
 fi
 
 CMD+=(-append "${APPEND[*]}")