-    Fix compiler warning in 80003es2lan.c
-    Add return value handler for e1000_*_kmrn_reg_80003es2lan
-    Fix usage of DEBUGOUT
-    Remove unnecessary variable initializations.
-    Removed unused variables (complaints from gcc).
-    Edit defines in 82571.h.
-    Add workaround for igb hw errata.
-    Shared code changes for Skylake/I219 support.
-    Remove unused OBFF and LTR functions.

Differential Revision:	https://reviews.freebsd.org/D3162
Submitted by:	erj
MFC after:	1 month
Sponsored by:	Intel Corporation