sim: Add a << overload for the Port class which prints its name.

sim: Add a << overload for the Port class which prints its name.

This makes it easier/less verbose to print the name of a port, it's
most important and identifying feature, in a DPRINTF or other stream
based output.

Change-Id: I050d102844612577f9a83d550e619736507a6781
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20234
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>