fs: reduce the use of module.h wherever possible

For files only using THIS_MODULE and/or EXPORT_SYMBOL, map
them onto including export.h -- or if the file isn't even
using those, then just delete the include.  Fix up any implicit
include dependencies that were being masked by module.h along
the way.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 5b4a936..92fcb19 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -14,7 +14,7 @@
  */
 
 #include <linux/kernel.h>
-#include <linux/module.h>
+#include <linux/export.h>
 #include <linux/spinlock.h>
 #include <linux/slab.h>
 #include <linux/sched.h>