According to the ib spec:
If the CI supports the Base Memory Management Extensions defined in this
specification, the L_Key format must consist of:
24 bit index in the most significant bits of the R_Key, and
8 bit key in the least significant bits of the R_Key
Through a successful Allocate L_Key verb invocation, the CI must let the
consumer own the key portion of the returned R_Key

Therefore, when creating a mkey using DEVX, the consumer is allowed to
change the key part. The kernel should compare only the index part of a
R_Key to determine equality with another R_Key.

Adding capability in order not to break backward compatibility.

Fixes: 534fd7aa ("IB/mlx5: Manage indirection mkey upon DEVX flow for ODP")
Link: https://lore.kernel.org/r/3d669aacea85a3a15c3b3b953b3eaba3f80ef9be.1659255945.git.leonro@nvidia.comSigned-off-by: Aharon Landau <aharonl@nvidia.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>