Add shift_overflow() helper to assist driver authors in ensuring that
shift operations don't cause overflows or other odd conditions.
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>
Signed-off-by: NLeon Romanovsky <leonro@mellanox.com>
[kees: tweaked comments and commit log, dropped unneeded assignment]
Signed-off-by: NKees Cook <keescook@chromium.org>