target/arm7tdmi: fix memory leak of register cache

There is no method to free the register cache, allocated in
arm7tdmi_init_target(), so we get a memory leak.
Issue identified by tracking all calls to arm_build_reg_cache().

Implement the method arm7tdmi_deinit_target() that in turn calls
arm7tdmi_free_reg_cache().

NOT TESTED on a real arm7tdmi target.
Tested on a arm926ejs (SPEAr320) by hacking the target type and
pretending it is a arm7tdmi:
	sed -i s/arm926ejs/arm7tdmi/ tcl/target/spear3xx.cfg

Change-Id: Iad465b708eb4ebb298725d7155fea76357e9045c
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5696
Tested-by: jenkins

src/target/arm7tdmi.c

@@ -613,6 +613,13 @@ static void arm7tdmi_build_reg_cache(struct target *target)
 	(*cache_p) = arm_build_reg_cache(target, arm);
 }
 
+static void arm7tdmi_free_reg_cache(struct target *target)
+{
+	struct arm *arm = target_to_arm(target);
+
+	arm_free_reg_cache(arm);
+}
+
 int arm7tdmi_init_target(struct command_context *cmd_ctx, struct target *target)
 {
 	arm7tdmi_build_reg_cache(target);
@@ -620,6 +627,11 @@ int arm7tdmi_init_target(struct command_context *cmd_ctx, struct target *target)
 	return ERROR_OK;
 }
 
+void arm7tdmi_deinit_target(struct target *target)
+{
+	arm7tdmi_free_reg_cache(target);
+}
+
 int arm7tdmi_init_arch_info(struct target *target,
 		struct arm7_9_common *arm7_9, struct jtag_tap *tap)
 {
@@ -718,6 +730,7 @@ struct target_type arm7tdmi_target = {
 	.commands  = arm7_9_command_handlers,
 	.target_create  = arm7tdmi_target_create,
 	.init_target = arm7tdmi_init_target,
+	.deinit_target = arm7tdmi_deinit_target,
 	.examine = arm7_9_examine,
 	.check_reset = arm7_9_check_reset,
 };

src/target/arm7tdmi.h

@@ -28,5 +28,6 @@ int arm7tdmi_init_arch_info(struct target *target,
 		struct arm7_9_common *arm7_9, struct jtag_tap *tap);
 int arm7tdmi_init_target(struct command_context *cmd_ctx,
 		struct target *target);
+void arm7tdmi_deinit_target(struct target *target);
 
 #endif /* OPENOCD_TARGET_ARM7TDMI_H */