hpet: Remove unused PCI Vendor ID #define

HPET_ID_VENDOR_8086 is defined but never used.  It would be a redefine
of PCI_VENDOR_ID_INTEL if it was ever used.

Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>