This patch fixes the issue with HPET on some platforms.

According to Vojtech Pavlik:

The first write after writing TN_SETVAL to the config register sets the
counter value, the second write sets the threshold.

When you only do the first write you never set the threshold and interrupts
won't be generated properly.

Thanks to John Stultz and Andrew Walrond for reporting, root causing the
issue and verifying this fix.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>