ice: enable FW logging

Once users have configured the FW logging then allow them to enable it
by writing to the 'fwlog/enable' file. The file accepts a boolean value
(0 or 1) where 1 means enable FW logging and 0 means disable FW logging.

  # echo <value> > /sys/kernel/debug/ice/0000\:18\:00.0/fwlog/enable

Where <value> is 0 or 1.

The user can read the 'fwlog/enable' file to see whether logging is
enabled or not. Reading the actual data is a separate patch. To see the
current value then:

  # cat /sys/kernel/debug/ice/0000\:18\:00.0/fwlog/enable

Signed-off-by: Paul M Stillwell Jr <paul.m.stillwell.jr@intel.com>
Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>