s390/mm: use correct unlock function in gmap_ipte_notify

The page table lock is acquired with a call to get_locked_pte,
replace the plain spin_unlock with the correct unlock function
pte_unmap_unlock.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/mm/pgtable.c

@@ -762,7 +762,7 @@ int gmap_ipte_notify(struct gmap *gmap, unsigned long gaddr, unsigned long len)
 			gaddr += PAGE_SIZE;
 			len -= PAGE_SIZE;
 		}
-		spin_unlock(ptl);
+		pte_unmap_unlock(ptep, ptl);
 	}
 	up_read(&gmap->mm->mmap_sem);
 	return rc;