x86, hyperv: Bypass the timer_irq_works() check

x86, hyperv: Bypass the timer_irq_works() check

commit ca3ba2a2f4a49a308e7d78c784d51b2332064f15 upstream.

This patch bypass the timer_irq_works() check for hyperv guest since:

- It was guaranteed to work.
- timer_irq_works() may fail sometime due to the lpj calibration were inaccurate
  in a hyperv guest or a buggy host.

In the future, we should get the tsc frequency from hypervisor and use preset
lpj instead.

[ hpa: I would prefer to not defer things to "the future" in the future... ]

Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Acked-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Link: http://lkml.kernel.org/r/1393558229-14755-1-git-send-email-jasowang@redhat.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>