ACPI problem in HP omnibook 6000 laptop

[Chen Lihong]

I cvsup-ed 5-stable code today and build world and kernel.
Before today's code only reboot doesn't work, now it can't boot well,
the laptop will hang after kernel loaded.
That maybe the laptop's problem, because in Windows XP the laptop will
also hang often. But the laptop works very well in 5-stable before
(except reboot 'shutdown -r now' or 'reboot').

/Lihong