vmalloc: remove vmalloc_sync_all() from alloc_vm_area()

There's no need for it: it will get faulted into the current pagetable
as needed.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

mm/vmalloc.c

@@ -2148,10 +2148,6 @@ struct vm_struct *alloc_vm_area(size_t size)
 		return NULL;
 	}
 
-	/* Make sure the pagetables are constructed in process kernel
-	   mappings */
-	vmalloc_sync_all();
-
 	return area;
 }
 EXPORT_SYMBOL_GPL(alloc_vm_area);