Kernel: Harvest randomness from various drivers

Random now gets entropy from the following drivers:
- KeyboardDevice
- PATAChannel
- PS2MouseDevice
- E1000NetworkAdapter
- RTL8139NetworkAdapter

Of these devices,  PS2MouseDevice and PATAChannel provide the vast
majority of the entropy.

Kernel/Net/E1000NetworkAdapter.cpp

@@ -204,6 +204,9 @@ void E1000NetworkAdapter::handle_irq(const RegisterState&)
     out32(REG_INTERRUPT_MASK_CLEAR, 0xffffffff);
 
     u32 status = in32(REG_INTERRUPT_CAUSE_READ);
+
+    m_entropy_source.add_random_event(status);
+
     if (status & 4) {
         u32 flags = in32(REG_CTRL);
         out32(REG_CTRL, flags | ECTRL_SLU);