i40e: field get conversion

Refactor the i40e driver to use FIELD_GET() for mask and shift reads,
which reduces lines of code and adds clarity of intent.

This code was generated by the following coccinelle/spatch script and
then manually repaired.

While making one of the conversions, an if() check was inverted to
return early and avoid un-necessary indentation of the remainder of the
function. In some other cases a stack variable was moved inside the
block where it was used while doing cleanups/review.

A couple places were changed to use le16_get_bits() instead of FIELD_GET
with a le16_to_cpu combination.

@get@
constant shift,mask;
metavariable type T;
expression a;
@@
-(((T)(a) & mask) >> shift)
+FIELD_GET(mask, a)

and applied via:
spatch --sp-file field_prep.cocci --in-place --dir \
 drivers/net/ethernet/intel/

Cc: Julia Lawall <Julia.Lawall@inria.fr>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Reviewed-by: Marcin Szycik <marcin.szycik@linux.intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@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>