net: macsec: move some definitions in a dedicated header

This patch moves some structure, type and identifier definitions into a
MACsec specific header. This patch does not modify how the MACsec code
is running and only move things around. This is a preparation for the
future MACsec hardware offloading support, which will re-use those
definitions outside macsec.c.

Change-Id: If052b8bf048951d915ea9def85512adb41b20520
Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Git-commit: c0e4eadfb8daf2e9557c7450f9b237c08b404419
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[quic_krudrapa@quicinc.com: Fixed merge conflicts]
Signed-off-by: Karthik Rudrapatna <quic_krudrapa@quicinc.com>