lib/interval_tree.c: simplify includes

The file uses nothing from init.h, and also doesn't need the full module.h
machinery; export.h is sufficient.  The latter requires the user to ensure
compiler.h is included, so do that explicitly instead of relying on some
other header pulling it in.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/interval_tree.c

-#include <linux/init.h>
 #include <linux/interval_tree.h>
 #include <linux/interval_tree_generic.h>
-#include <linux/module.h>
+#include <linux/compiler.h>
+#include <linux/export.h>
 
 #define START(node) ((node)->start)
 #define LAST(node)  ((node)->last)