arch,base,mem,sim: Fix style in base/types.hh and remove extra includes.

arch,base,mem,sim: Fix style in base/types.hh and remove extra includes.

The base/refcnt.hh header was not used in base/types.hh at all, and
enum/ByteOrder.hh was there just so other files could find it. Instead,
this change moves enum/Byteorder.hh to sim/byteswap.hh where it's fits
with the purpose of the header.

This change also fixes some style problems with the code in
base/types.hh itself.

Change-Id: I471ae5cb2cca9169ba8616fb8411b40108a3ffb2
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/39855
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>