Add checkpatch.pl to presubmit tests.

Change-Id: I235ea140f5f54dc8b22f1c69dcff5e99a34ff602
diff --git a/src/vm.c b/src/vm.c
index 4a14eae..40aa294 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -76,6 +76,7 @@
 void vm_start_vcpu(struct vm *vm, size_t index, ipaddr_t entry, uintreg_t arg)
 {
 	struct vcpu *vcpu = &vm->vcpus[index];
+
 	if (index < vm->vcpu_count) {
 		arch_regs_set_pc_arg(&vcpu->regs, entry, arg);
 		vcpu_on(vcpu);