PCI: hv: Temporary own CPU-number-to-vCPU-number infra

To ease parallel effort to centralize CPU-number-to-vCPU-number conversion,
temporarily stand up own version, file-local hv_tmp_cpu_nr_to_vp_nr().
Once the changes have merged, this work-around can be removed, and the
calls replaced with hv_cpu_number_to_vp_number().

Signed-off-by: Jork Loeser <jloeser@microsoft.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
Acked-by: K. Y. Srinivasan <kys@microsoft.com>