jtag/core: honour SRST timings in SWD mode

Since SWD is currently abusing the JTAG command queue for reset and
sleep handling (and all other operations are performed in a different
way), sleep needs to be forced explicitly to ensure correct timings.

Change-Id: I5b0da6cbb7d0560154e4077b261aa6828cefc892
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Reviewed-on: http://openocd.zylin.com/2591
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>

src/jtag/core.c

@@ -649,6 +649,12 @@ void swd_add_reset(int req_srst)
 			if (adapter_nsrst_delay)
 				jtag_add_sleep(adapter_nsrst_delay * 1000);
 		}
+
+		retval = jtag_execute_queue();
+		if (retval != ERROR_OK) {
+			LOG_ERROR("SRST timings error");
+			return;
+		}
 	}
 }