linux/pagemap.h: Fixed a typo in a code comment.

Corrected a minor typo in a code comment where 'be' was missing.

Signed-off-by: Raymond L. Rivera <ray.l.rivera@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index e1474ae..bf657ff 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -96,7 +96,7 @@
 }
 
 /*
- * The page cache can done in larger chunks than
+ * The page cache can be done in larger chunks than
  * one page, because it allows for more efficient
  * throughput (it can then be mapped into user
  * space in smaller chunks for same flexibility).