libnvdimm: Cleanup include of badblocks.h

* drivers/nvdimm/core.c doesn't use anything from badblocks.h on its own,
thus including it isn't needed. There's indeed indirect use, via funcs
in nd.h, but this one already includes badblocks.h.

* drivers/nvdimm/claim.c calls stuff from badblocks.h and therefore should
include it on its own (instead of relying any other header doing that)

* drivers/nvdimm/btt.h doesn't really need anything from badblocks.h and
can easily live with a forward declaration of struct badblocks (just
having pointers to it, but not dereferencing it anywhere)

Signed-off-by: Enrico Weigelt <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dan Williams <[e-mail]>

drivers/nvdimm/btt.h

···
 #ifndef _LINUX_BTT_H
 #define _LINUX_BTT_H
 
-#include <linux/badblocks.h>
 #include <linux/types.h>
 
 #define BTT_SIG_LEN 16
···
 	struct mutex err_lock;
 	int log_index[2];
 };
+
+struct badblocks;
 
 /**
  * struct btt - handle for a BTT instance

drivers/nvdimm/claim.c

···
  */
 #include <linux/device.h>
 #include <linux/sizes.h>
+#include <linux/badblocks.h>
 #include "nd-core.h"
 #include "pmem.h"
 #include "pfn.h"

drivers/nvdimm/core.c

···
  * Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
  */
 #include <linux/libnvdimm.h>
-#include <linux/badblocks.h>
 #include <linux/suspend.h>
 #include <linux/export.h>
 #include <linux/module.h>