ice: use static inline for dummy functions

Trivial:
The driver had previously attempted to use #define
macros to make functions that have no use in certain
configs disappear. Using static inlines instead allows
for certain static checkers to process the code better,
and results in no functional change.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Tony Brelinski <tonyx.brelinski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

ice: Implement DCBNL support

Implement interface layer for the DCBNL subsystem. These are the functions
to support the callbacks defined in the dcbnl_rtnl_ops struct. These
callbacks are going to be used to interface with the DCB settings of the
device. Implementation of dcb_nl set functions and supporting SW DCB
functions.

Signed-off-by: Dave Ertman <david.m.ertman@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>