mm/filemap.c: remove include of hardirq.h

in_atomic() has been moved to include/linux/preempt.h, and the filemap.c
doesn't use in_atomic() directly at all, so it sounds unnecessary to
include hardirq.h.

Link: http://lkml.kernel.org/r/1509985319-38633-1-git-send-email-yang.s@alibaba-inc.com
Signed-off-by: Yang Shi <yang.s@alibaba-inc.com>
Reviewed-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/filemap.c

@@ -31,7 +31,6 @@
 #include <linux/blkdev.h>
 #include <linux/security.h>
 #include <linux/cpuset.h>
-#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
 #include <linux/hugetlb.h>
 #include <linux/memcontrol.h>
 #include <linux/cleancache.h>