This is in-kernel C code, so there is no reason to use _BITUL().
Replace it with equivalent BIT().

I added #include <linux/bits.h> explicitly although it has been included
by other headers eventually.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>