target: less implicit inclusion of "etm.h"

Don't include it in more headers than necessary; just
use it in the few files that actually need it.

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

src/target/arm7_9_common.c

@@ -34,6 +34,7 @@
 #include "embeddedice.h"
 #include "target_request.h"
 #include "arm7_9_common.h"
+#include "etm.h"
 #include "time_support.h"
 #include "arm_simulator.h"
 #include "algorithm.h"