target: no implicit #includes of "register.h"

Same deal:  "register.h" got needlessly included all over the
place because of being in a few widely included headers.

So take it out of the header files which included it, and put
it in files which use it ... reduce needless interdependencies.

Also, don't need that extra "types.h" inclusion.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

src/target/mips32.h

@@ -24,7 +24,6 @@
 #define MIPS32_H
 
 #include "target.h"
-#include "register.h"
 #include "mips32_pracc.h"