include/linux/radix-tree.h: remove unneeded #include <linux/bug.h>

include/linux/radix-tree.h: remove unneeded #include <linux/bug.h>

This include was added by commit 07b6189f5fa1 ("BUG: headers with
BUG/BUG_ON etc. need linux/bug.h") because BUG_ON() was used in this
header at that time.

Some time later, commit 724999618099 ("lib: radix-tree: check accounting
of existing slot replacement users") removed the use of BUG_ON() from
this header.

Since then, there is no reason to include <linux/bug.h>.

Link: http://lkml.kernel.org/r/1505660151-4383-1-git-send-email-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Chris Mi <chrism@mellanox.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>