arm_adi_v5: Add a back-pointer from an AP to its DAP

This will make it possible to reference directly the AP used for debug
in the target instance and remove the DAP reference. This will in turn
enable getting rid of the need to select an "active" AP in the DAP (using
dap apsel).

Change-Id: I265846a427c714204f4fd3df3cdb75843686c2d0
Signed-off-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Reviewed-on: http://openocd.zylin.com/3144
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>

src/target/arm_adi_v5.h

@@ -127,6 +127,16 @@
  * Most common is a MEM-AP, for memory access.
  */
 struct adiv5_ap {
+	/**
+	 * DAP this AP belongs to.
+	 */
+	struct adiv5_dap *dap;
+
+	/**
+	 * Number of this AP.
+	 */
+	uint8_t ap_num;
+
 	/**
 	 * Default value for (MEM-AP) AP_REG_CSW register.
 	 */