refactor(port): move netlink to a new file

[glimchb]

Signed-off-by: Boris Glimcher Boris.Glimcher@emc.com

[codecov]

Codecov Report

Merging #274 (3ac043d) into main (800603a) will increase coverage by 0.29%.
The diff coverage is 84.53%.

@@            Coverage Diff             @@
##             main     #274      +/-   ##
==========================================
+ Coverage   61.18%   61.48%   +0.29%     
==========================================
  Files          27       28       +1     
  Lines        1837     1851      +14     
==========================================
+ Hits         1124     1138      +14     
  Misses        609      609              
  Partials      104      104              

Files	Coverage Δ
pkg/bridge/netlink.go	100.00% <100.00%> (ø)
pkg/port/grpc.go	57.71% <100.00%> (-8.37%)	⬇️
pkg/svi/frr.go	17.64% <ø> (ø)
pkg/svi/netlink.go	100.00% <100.00%> (ø)
pkg/vrf/frr.go	30.76% <ø> (ø)
pkg/vrf/netlink.go	92.85% <ø> (ø)
pkg/port/netlink.go	83.87% <83.87%> (ø)