[kernel] Don't unmask IOAPIC IRQs immediately

The amount of spurious IRQ activity on real hardware severely slows down
the system (minutes per frame instead of frames per second). There's no
reason to unmask all of them from the get-go before they're set up to be
handled.

src/kernel/device_manager.cpp

@@ -63,7 +63,7 @@ void irq4_callback(void *)
 
 
 device_manager::device_manager() :
-	m_lapic(0)
+	m_lapic(nullptr)
 {
 	m_irqs.ensure_capacity(32);
 	m_irqs.set_size(16);
@@ -236,12 +236,14 @@ device_manager::load_apic(const acpi_apic *apic)
 		p += length;
 	}
 
+	/*
 	for (uint8_t i = 0; i < m_ioapics[0].get_num_gsi(); ++i) {
 		switch (i) {
 			case 2: break;
 			default: m_ioapics[0].mask(i, false);
 		}
 	}
+	*/
 
 	m_lapic->enable();
 }