mlxsw: core_linecards: Expose HW revision and INI version

Implement info_get() to expose HW revision of a linecard and loaded INI
version.

Example:

$ devlink dev info auxiliary/mlxsw_core.lc.0
auxiliary/mlxsw_core.lc.0:
  versions:
      fixed:
        hw.revision 0
      running:
        ini.version 4

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

Documentation/networking/devlink/mlxsw.rst

@@ -58,6 +58,24 @@ The ``mlxsw`` driver reports the following versions
      - running
      - Three digit firmware version
 
+Line card auxiliary device info versions
+========================================
+
+The ``mlxsw`` driver reports the following versions for line card auxiliary device
+
+.. list-table:: devlink info versions implemented
+   :widths: 5 5 90
+
+   * - Name
+     - Type
+     - Description
+   * - ``hw.revision``
+     - fixed
+     - The hardware revision for this line card
+   * - ``ini.version``
+     - running
+     - Version of line card INI loaded
+
 Driver-specific Traps
 =====================