include: Remove pagemap.h from blkdev.h

My UEK-derived config has 1030 files depending on pagemap.h before
this change.  Afterwards, just 240 files need to be rebuilt when I
touch pagemap.h.  I think blkdev.h is probably included too widely,
but untangling that dependency is harder and this solves my problem.
x86 allmodconfig builds, but there may be implicit include problems
on other architectures.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

block/blk-settings.c

@@ -7,6 +7,7 @@
 #include <linux/init.h>
 #include <linux/bio.h>
 #include <linux/blkdev.h>
+#include <linux/pagemap.h>
 #include <linux/memblock.h>	/* for max_pfn/max_low_pfn */
 #include <linux/gcd.h>
 #include <linux/lcm.h>

drivers/block/brd.c

@@ -18,6 +18,7 @@
 #include <linux/bio.h>
 #include <linux/highmem.h>
 #include <linux/mutex.h>
+#include <linux/pagemap.h>
 #include <linux/radix-tree.h>
 #include <linux/fs.h>
 #include <linux/slab.h>

drivers/block/loop.c

@@ -53,6 +53,7 @@
 #include <linux/moduleparam.h>
 #include <linux/sched.h>
 #include <linux/fs.h>
+#include <linux/pagemap.h>
 #include <linux/file.h>
 #include <linux/stat.h>
 #include <linux/errno.h>

drivers/md/bcache/super.c

@@ -16,6 +16,7 @@
 #include "features.h"
 
 #include <linux/blkdev.h>
+#include <linux/pagemap.h>
 #include <linux/debugfs.h>
 #include <linux/genhd.h>
 #include <linux/idr.h>

drivers/nvdimm/btt.c

@@ -6,6 +6,7 @@
 #include <linux/highmem.h>
 #include <linux/debugfs.h>
 #include <linux/blkdev.h>
+#include <linux/pagemap.h>
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/mutex.h>

drivers/nvdimm/pmem.c

@@ -8,6 +8,7 @@
  */
 
 #include <linux/blkdev.h>
+#include <linux/pagemap.h>
 #include <linux/hdreg.h>
 #include <linux/init.h>
 #include <linux/platform_device.h>

drivers/scsi/scsicam.c

@@ -17,6 +17,7 @@
 #include <linux/genhd.h>
 #include <linux/kernel.h>
 #include <linux/blkdev.h>
+#include <linux/pagemap.h>
 #include <linux/msdos_partition.h>
 #include <asm/unaligned.h>
 

include/linux/blkdev.h

@@ -11,7 +11,6 @@
 #include <linux/minmax.h>
 #include <linux/timer.h>
 #include <linux/workqueue.h>
-#include <linux/pagemap.h>
 #include <linux/backing-dev-defs.h>
 #include <linux/wait.h>
 #include <linux/mempool.h>