Sweep away N/A fw_version dustbunnies from the .get_drvinfo routine of a number of drivers

Per discussion with Ben Hutchings and David Miller, go through and
remove assignments of "N/A" to fw_version in various drivers'
.get_drvinfo routines.  While there clean-up some use of bare
constants and such.

Signed-off-by: Rick Jones <rick.jones2@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>