mlxsw: reg: Add XM Lookup Table Query Register

The XLTQ is used to query HW for XM-related info.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>