KVM: SVM: Use svm_get_lbr_vmcb() helper to handle writes to DEBUGCTL

Use the recently introduced svm_get_lbr_vmcb() instead an open coded
equivalent to retrieve the target VMCB when emulating writes to
MSR_IA32_DEBUGCTLMSR.

No functional change intended.

Link: https://lore.kernel.org/r/20230607203519.1570167-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/kvm/svm/svm.c

@@ -3052,13 +3052,8 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 		if (data & DEBUGCTL_RESERVED_BITS)
 			return 1;
 
-		if (svm->vmcb->control.virt_ext & LBR_CTL_ENABLE_MASK)
-			svm->vmcb->save.dbgctl = data;
-		else
-			svm->vmcb01.ptr->save.dbgctl = data;
-
+		svm_get_lbr_vmcb(svm)->save.dbgctl = data;
 		svm_update_lbrv(vcpu);
-
 		break;
 	case MSR_VM_HSAVE_PA:
 		/*