ice: do not clutter debug logs with unused data

Currently, debug logs are unnecessarily cluttered with the contents of
command data buffers even if the receiver of that command (i.e. FW or MBX)
are not told to read the buffer.  Change to only log command data buffers
when the RD flag (indicates receiver needs to read the buffer) is set.
Continue to log response data buffer when the returned datalen is non-zero.

Also, rename a local variable to reflect what is in the hardware
specification and how it is used elsewhere in the code, use local variables
instead of duplicating endian conversions unnecessarily and remove an
unnecessary assignment.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@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>