Kernel/Interrupts: Return boolean on whether we handled the interrupt

If we are in a shared interrupt handler, the called handlers might
indicate it was not their interrupt, so we should not increment the
call counter of these handlers.

Kernel/Storage/AHCI.h

@@ -158,6 +158,11 @@ public:
         return m_bitfield & ((1 << port_index) & m_bit_mask);
     }
 
+    bool is_zeroed() const
+    {
+        return (m_bitfield & m_bit_mask) == 0;
+    }
+
     Vector<u8> to_vector() const
     {
         // FIXME: Add a sync mechanism!