[PATCH] pa-risc: kernel/fork.c broken by the new rmap

Any architecture (like pa-risc) that makes use of the helper function
flush_dcache_mmap_lock() won't compile with the new rmap due to use of
the wrong "mapping". 

Trivial fix.

kernel/fork.c

@@ -333,9 +333,9 @@ static inline int dup_mmap(struct mm_struct * mm, struct mm_struct * oldmm)
       
 			/* insert tmp into the share list, just after mpnt */
 			spin_lock(&file->f_mapping->i_mmap_lock);
-			flush_dcache_mmap_lock(mapping);
+			flush_dcache_mmap_lock(file->f_mapping);
 			vma_prio_tree_add(tmp, mpnt);
-			flush_dcache_mmap_unlock(mapping);
+			flush_dcache_mmap_unlock(file->f_mapping);
 			spin_unlock(&file->f_mapping->i_mmap_lock);
 		}