Use IRQ2 for HPET.

[todo]

Idealy, HPET should be using IRQ2 (which seems to be generally wired properly). Unfortunately, qemu has an unfortunate bug where interrupts for IRQ2 gets ignored.
As a workaround, we currently use IRQ16 as the timer IRQ. This is not very portable - but it'll do until we have a proper IRQ allocation scheme.
Upstream bug: https://bugs.launchpad.net/qemu/+bug/1834051

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SunriseOS/kernel/src/devices/hpet.rs

Lines 514 to 524 in 4f01071

	// TODO: Use IRQ2 for HPET.
	// BODY: Idealy, HPET should be using IRQ2 (which seems to be generally
	// BODY: wired properly). Unfortunately, qemu has an unfortunate bug where
	// BODY: interrupts for IRQ2 gets ignored.
	// BODY:
	// BODY: As a workaround, we currently use IRQ16 as the timer IRQ. This is
	// BODY: not very portable - but it'll do until we have a proper IRQ
	// BODY: allocation scheme.
	// BODY:
	// BODY: Upstream bug: https://bugs.launchpad.net/qemu/+bug/1834051
	// Route the timer to the IRQ 16. IRQ 2 is broken, and IRQ 0 is not

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This issue was generated by todo based on a TODO comment in 4f01071 when #348 was merged. cc @roblabla.