Drivers: hv: hv_util: Avoid dynamic allocation in time synch

Under stress, we have seen allocation failure in time synch code. Avoid
this dynamic allocation.

Signed-off-by: Vivek Yadav <vyadav@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>