Clean up #includes

Result of running IWYU (https://include-what-you-use.org/) and
applying most of the suggestions about unncessary includes and
forward declarations.

Was motivated by observing that <thread> was being included in
ppcopcodes.cpp even though it was unused (found while researching
the use of threads), but seems generally good to help with build
times and correctness.

devices/memctrl/memctrlbase.cpp

@@ -20,6 +20,7 @@ along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 
 #include <devices/memctrl/memctrlbase.h>
+#include <devices/common/mmiodevice.h>
 
 #include <algorithm>    // to shut up MSVC errors (:
 #include <cstring>