ptp: ocp: Rename version string shown by devlink.

The TimeCard has two FPGA images in the flash: the actual firmware,
and a manufacturing fallback version which is intended to act as a
loader in case the flash update failed.

Name these "fw" and "loader", which are reflected in devlink:

    [root@timecard drv]# devlink dev info
    pci/0000:04:00.0:
      driver ptp_ocp
      serial_number fc:c2:3d:2e:d7:c0
      versions:
          running:
            fw 5

Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>