radix-tree: add an explicit include of bitops.h

The radix-tree header uses the __ffs() function, which is defined in
bitops.h. The current kernel headers implicitly include bitops.h, but
the userspace test harness does not.

Signed-off-by: Matthew Wilcox <[e-mail]>
Cc: Johannes Weiner <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Cc: "Kirill A. Shutemov" <[e-mail]>
Cc: Ross Zwisler <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/radix-tree.h

···
 #ifndef _LINUX_RADIX_TREE_H
 #define _LINUX_RADIX_TREE_H
 
+#include <linux/bitops.h>
 #include <linux/preempt.h>
 #include <linux/types.h>
 #include <linux/bug.h>