KVM: arm64: Fix __pkvm_host_mkyoung_guest() return value

Don't use an uninitialised stack variable, and just return 0
on the non-error path.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202502100911.8c9DbtKD-lkp@intel.com/
Reviewed-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: Marc Zyngier

arch/arm64/kvm/hyp/nvhe/mem_protect.c

@@ -1073,7 +1073,6 @@ int __pkvm_host_mkyoung_guest(u64 gfn, struct pkvm_hyp_vcpu *vcpu)
 {
 	struct pkvm_hyp_vm *vm = pkvm_hyp_vcpu_to_hyp_vm(vcpu);
 	u64 ipa = hyp_pfn_to_phys(gfn);
-	int ret;
 
 	if (pkvm_hyp_vm_is_protected(vm))
 		return -EPERM;
@@ -1083,5 +1082,5 @@ int __pkvm_host_mkyoung_guest(u64 gfn, struct pkvm_hyp_vcpu *vcpu)
 	kvm_pgtable_stage2_mkyoung(&vm->pgt, ipa, 0);
 	guest_unlock_component(vm);
 
-	return ret;
+	return 0;
 }