RDMA/uverbs: Restrict usage of privileged QKEYs

RDMA/uverbs: Restrict usage of privileged QKEYs

According to the IB specification rel-1.6, section 3.5.3:
"QKEYs with the most significant bit set are considered controlled
QKEYs, and a HCA does not allow a consumer to arbitrarily specify a
controlled QKEY."

Thus, block non-privileged users from setting such a QKEY.

Cc: stable@vger.kernel.org
Fixes: bc38a6abdd5a ("[PATCH] IB uverbs: core implementation")
Signed-off-by: Edward Srouji <edwards@nvidia.com>
Link: https://lore.kernel.org/r/c00c809ddafaaf87d6f6cb827978670989a511b3.1685960567.git.leon@kernel.org
Signed-off-by: Leon Romanovsky <leon@kernel.org>