xtensa: don't clear cpenable unconditionally on release

fast_coprocessor exception handler expects that the coprocessor owner task never gets the "coprocessor disabled" exception for a coprocessor that is marked as enabled in the thread_info::cpenable. If that happens it will reload potentially outdated context from the thread_info structure into the coprocessor registers.
Only call coprocessor_clear_cpenable from the coprocessor_release_all if the latter is called for the current task.

---
 arch/xtensa/kernel/process.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

index 3fa0c440f664..6c7c80106f60 100644
@@ -87,7 +87,8 @@ void coprocessor_release_all(struct thread_info *ti)
 	}
 
 	ti->cpenable = cpenable;
-	coprocessor_clear_cpenable();
+	if (ti == current_thread_info())
+		coprocessor_clear_cpenable();
 
 	preempt_enable();
 }

2.11.0

After looking at it some more I see that the above is not true. It will flush current coprocessor context to the thread_info and then load it back from there. No correctness issue, but some extra work that can be avoided.

Thanks.
-- Max