radix-tree.h: remove unneeded include of kernel.h

It seems that we can remove the unneeded include of kernel.h from radix-tree.h safely. Any user of radix-tree that need kernel.h should include it separately.

---
 include/linux/radix-tree.h |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

index ffc444c..34be4b1 100644
@@ -24,7 +24,6 @@
 #include <linux/preempt.h>
 #include <linux/types.h>
 #include <linux/bug.h>
-#include <linux/kernel.h>
 #include <linux/rcupdate.h>
 
 /*

1.7.3.4