sched/irq: Fix potential deadlock in irqchain_detach

Release g_irqchainlock before calling irq_detach to avoid holding two locks
simultaneously, which can cause thread deadlock.

The irqchain_detach function was calling irq_detach while holding g_irqchainlock,
and irq_detach attempts to acquire g_irqlock. This lock ordering violation could
lead to deadlock in multithreaded scenarios.

Fix:
- Move spin_unlock_irqrestore(&g_irqchainlock, flags) before irq_detach call
- Ensure locks are released in proper order to prevent circular wait

This is part of the irq_chain_lock feature for safer IRQ chain handling.

Signed-off-by: pangzhen1 <pangzhen1@xiaomi.com>

sched/irq/irq_chain.c

@@ -257,13 +257,14 @@ int irqchain_detach(int irq, xcpt_t isr, FAR void *arg)
                   break;
                 }
             }
+
+          spin_unlock_irqrestore(&g_irqchainlock, flags);
         }
       else
         {
+          spin_unlock_irqrestore(&g_irqchainlock, flags);
           ret = irq_detach(irq);
         }
-
-      spin_unlock_irqrestore(&g_irqchainlock, flags);
     }
 
   return ret;