i40e: inline interrupt enable

i40e: inline interrupt enable

Orabug: 22342532

The interrupt enable function can be inlined by moving it to the header
file, which decreases the function call overhead for a frequently called
function.

Change-ID: I3214cc99593725768642680e7b8ce7e9bba7e44d
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
(cherry picked from commit 02d109be3ddc9768c1c38709218648d0c48a4ea9)
Signed-off-by: Brian Maly <brian.maly@oracle.com>