The reason of including <linux/bitops.h> here is just for BIT() macro.

Since commit 8bd9cb51 ("locking/atomics, asm-generic: Move some
macros from <linux/bitops.h> to a new <linux/bits.h> file"),
<linux/bits.h> is enough for such compile-time macros.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>