target/esp_xtensa: add xtensa on_halt handler

Right after target halt, some activities needs to be done
such as printing exception reason, disable wdts and reading
debug stubs information.
Missing activities will be submitted in the next patches.

Signed-off-by: Erhan Kurubas <erhan.kurubas@espressif.com>
Change-Id: I27aad5614d903f4bd7c8d6dba6bfb0bdb93ed8dc
Reviewed-on: https://review.openocd.org/c/openocd/+/7757
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Tested-by: jenkins

src/target/espressif/esp_xtensa.c

@@ -17,6 +17,12 @@
 #include "esp_xtensa.h"
 #include "esp_semihosting.h"
 
+int esp_xtensa_on_halt(struct target *target)
+{
+	/* will be used in the next patches */
+	return ERROR_OK;
+}
+
 int esp_xtensa_init_arch_info(struct target *target,
 	struct esp_xtensa_common *esp_xtensa,
 	struct xtensa_debug_module_config *dm_cfg,