armv7m: add generic trace support (TPIU, ITM, etc.)

This provides support for various trace-related subsystems in a
generic and expandable way.

Change-Id: I3a27fa7b8cfb111753088bb8c3d760dd12d1395f
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Reviewed-on: http://openocd.zylin.com/2538
Tested-by: jenkins

src/target/armv7m.c

@@ -635,6 +635,9 @@ int armv7m_init_arch_info(struct target *target, struct armv7m_common *armv7m)
 
 	armv7m->common_magic = ARMV7M_COMMON_MAGIC;
 	armv7m->fp_feature = FP_NONE;
+	armv7m->trace_config.trace_bus_id = 1;
+	/* Enable stimulus port #0 by default */
+	armv7m->trace_config.itm_ter[0] = 1;
 
 	arm->core_type = ARM_MODE_THREAD;
 	arm->arch_info = armv7m;