target/cortex_m: remove target halted check when removing a breakpoint

Remove the target halted check from cortex_m_remove_breakpoint()
as there is no such check in cortex_m_set_breakpoint() and bp can be
safely removed from the running target.

While on it return the error code from cortex_m_unset_breakpoint()
to higher level.

Change-Id: I2b358c3661feed84297913e9f589bdf1e4de7e64
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/4887


Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>
Reviewed-by: Jānis Skujenieks <janis.skujenieks@gmail.com>
Reviewed-by: Christopher Head <chead@zaber.com>

src/target/cortex_m.c

@@ -1288,16 +1288,10 @@ int cortex_m_add_breakpoint(struct target *target, struct breakpoint *breakpoint
 
 int cortex_m_remove_breakpoint(struct target *target, struct breakpoint *breakpoint)
 {
-	/* REVISIT why check? FPB can be updated with core running ... */
-	if (target->state != TARGET_HALTED) {
-		LOG_WARNING("target not halted");
-		return ERROR_TARGET_NOT_HALTED;
-	}
-
-	if (breakpoint->set)
-		cortex_m_unset_breakpoint(target, breakpoint);
+	if (!breakpoint->set)
+		return ERROR_OK;
 
-	return ERROR_OK;
+	return cortex_m_unset_breakpoint(target, breakpoint);
 }
 
 int cortex_m_set_watchpoint(struct target *target, struct watchpoint *watchpoint)