datapath-windows: Rename OvsGetVportNo into OvsComputeVportNo and make public

datapath-windows: Rename OvsGetVportNo into OvsComputeVportNo and make public

OvsGetVportNo computes a new port number. Therefore, OvsComputeVportNo
is a more clear name for what the function does. Reading OvsGetVportNo
may give the false impression that it returns the port number of an
existing vport.

Also, since the responsibility of assigning dp port numbers no longer
falls on the hyper-v switch port handlers side, but on the netlink vport
commands side (vport add), we will need to use this compute port number
function from outside Vport.c. Therefore, this function declaration is
moved from Vport.c to Vport.h, and becomes public.

Signed-off-by: Samuel Ghinet <sghinet@cloudbasesolutions.com>
Co-authored-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Acked-by: Ankur Sharma <ankursharma@vmware.com>
Acked-by: Eitan Eliahu <eliahue@vmware.com>
Acked-by: Nithin Raju <nithin@vmware.com>
Tested-by: Nithin Raju <nithin@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>