lib/radix-tree.c: change to simpler include

The comment helpfully explains why hardirq.h is included, but since
commit 2d4b84739f0a ("hardirq: Split preempt count mask definitions")
in_interrupt() has been provided by preempt_mask.h. Use that instead,
saving around 40 lines in the generated dependency file.

Signed-off-by: Rasmus Villemoes <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

lib/radix-tree.c

···
 #include <linux/string.h>
 #include <linux/bitops.h>
 #include <linux/rcupdate.h>
-#include <linux/hardirq.h>		/* in_interrupt() */
+#include <linux/preempt_mask.h>		/* in_interrupt() */
 
 
 /*