devlink: add macro for "fw.psid"

The "fw.psid" devlink info version is documented in devlink-info.rst,
and used by one driver. However, there is no associated macro for this
firmware version like there is for others. Add one now.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>