Kernel: Stub Spinlock is_locked on aarch64

Author: https://github.com/filiphsps
Commit: 4aaf38e4f7
Pull-request: https://github.com/SerenityOS/serenity/pull/14778
Reviewed-by: https://github.com/FireFox317
Reviewed-by: https://github.com/nico ✅
Reviewed-by: https://github.com/supercomputer7 ✅

Kernel/Arch/Spinlock.h

@@ -26,6 +26,10 @@ public:
 
     [[nodiscard]] ALWAYS_INLINE bool is_locked() const
     {
+        // FIXME: Implement Spinlock on aarch64
+#if ARCH(AARCH64)
+        return true;
+#endif
         return m_lock.load(AK::memory_order_relaxed) != 0;
     }