KVM: PPC: Book3S HV: Release lock on page-out failure path

When migrate_vma_setup() fails in kvmppc_svm_page_out(),
release kvm->arch.uvmem_lock before returning.

Fixes: ca9f4942 ("KVM: PPC: Book3S HV: Support for running secure guests")
Signed-off-by: Bharata B Rao <bharata@linux.ibm.com>
Reviewed-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

arch/powerpc/kvm/book3s_hv_uvmem.c

@@ -571,7 +571,7 @@ kvmppc_svm_page_out(struct vm_area_struct *vma, unsigned long start,
 
 	ret = migrate_vma_setup(&mig);
 	if (ret)
-		return ret;
+		goto out;
 
 	spage = migrate_pfn_to_page(*mig.src);
 	if (!spage || !(*mig.src & MIGRATE_PFN_MIGRATE))