Define generic___bitrev8/16/32 using the implementation in
<linux/bitrev.h>, so they can be reused in <asm/bitrev.h>,
such as RISCV.
Reviewed-by: Yury Norov <ynorov@nvidia.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Signed-off-by: Yury Norov <ynorov@nvidia.com>
