Btrfs: trivial include fixups

Almost none of the files including module.h need to do so,
remove them.

Include sched.h in extent-tree.c to silence a warning about cond_resched()
being undeclared.

Signed-off-by: Zach Brown <zach.brown@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 14b9326..5ace2c3 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -16,7 +16,7 @@
  * Boston, MA 021110-1307, USA.
  */
 
-#include <linux/module.h>
+#include <linux/sched.h>
 #include "ctree.h"
 #include "disk-io.h"
 #include "print-tree.h"