i40e/i40evf: Convert macro to static inline

Inline functions are preferred over macros when they can be used
interchangeably.

CC: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reported-by: Joe Perches <joe@perches.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>