x86: hpet clock enable quirk on nVidia nForce 430

this patch allows hpet=force on nVidia nForce 430 southbridge.
This patch was tested by me on my old Asus A8N-VM CSM (where bios does not
support hpet and does not advertise it via acpi entry). My nForce430 version:
lspci -nn | grep LPC
00:0a.0 ISA bridge [0601]: nVidia Corporation MCP51 LPC Bridge [10de:0260]
(rev a2)

Kernel 2.6.24.3 after patching and using hpet=force reports this:
dmesg | grep -i hpet
Kernel command line: root=/dev/sda8 ro vga=773 video=vesafb:mtrr:4,ywrap
vt.default_utf8=0 hpet=force
Force enabled HPET at base address 0xfed00000
hpet clockevent registered
Time: hpet clocksource has been installed.

grep -i hpet /proc/timer_list
Clock Event Device: hpet
 set_next_event: hpet_legacy_next_event
 set_mode:       hpet_legacy_set_mode

grep Clock /proc/timer_list (before patching)
Clock Event Device: pit
Clock Event Device: lapic

grep Clock /proc/timer_list (after patching)
Clock Event Device: hpet
Clock Event Device: lapic

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>