misc: Fix some includes

Fix some missing and extra includes around the codebase.

Change-Id: Ibf314b43a966943a8096958f68382e1e245f29e3
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/38738
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>

src/dev/serial/uart8250.cc

@@ -41,6 +41,7 @@
 #include "dev/platform.hh"
 #include "mem/packet.hh"
 #include "mem/packet_access.hh"
+#include "sim/serialize.hh"
 
 using namespace std;