Move from memset to memset_s.

This adds the extra bounds checks and panics if there is a violation.

Change-Id: I9db3ca44be4f9c39964d912b57fe7b68e2792bc1
diff --git a/src/cpu.c b/src/cpu.c
index b2213d1..ca26122 100644
--- a/src/cpu.c
+++ b/src/cpu.c
@@ -159,7 +159,7 @@
 
 void vcpu_init(struct vcpu *vcpu, struct vm *vm)
 {
-	memset(vcpu, 0, sizeof(*vcpu));
+	memset_s(vcpu, sizeof(*vcpu), 0, sizeof(*vcpu));
 	sl_init(&vcpu->lock);
 	vcpu->regs_available = true;
 	vcpu->vm = vm;