md: move lots of #include lines out of .h files and into .c

This makes the includes more explicit, and is preparation for moving
md_k.h to drivers/md/md.h

Remove include/raid/md.h as its only remaining use was to #include
other files.

Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/raid6.h b/drivers/md/raid6.h
index f6c13af..66e6b0c 100644
--- a/drivers/md/raid6.h
+++ b/drivers/md/raid6.h
@@ -17,11 +17,7 @@
 
 /* Set to 1 to use kernel-wide empty_zero_page */
 #define RAID6_USE_EMPTY_ZERO_PAGE 0
-
-#include <linux/raid/md.h>
-#include "raid5.h"
-
-typedef raid5_conf_t raid6_conf_t; /* Same configuration */
+#include <linux/blkdev.h>
 
 /* Additional compute_parity mode -- updates the parity w/o LOCKING */
 #define UPDATE_PARITY	4