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/etm.c

@@ -22,6 +22,7 @@
 #endif
 
 #include "armv4_5.h"
+#include "etm.h"
 #include "etb.h"
 #include "image.h"
 #include "arm_disassembler.h"