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>