x86: HPET force enable for CX700 / VIA Epia LT

Allow using HPET with the hpet=force command line option on VIA EPIA
CX700 systems.

Signed-off-by: Udo van den Heuvel <udovdh@xs4all.nl>
Cc: Robert Hancock <hancockrwd@gmail.com>
LKML-Reference:  <4C8F04DC.5060303@xs4all.nl>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>