datapath-windows: add WCHAR version of OvsFindVportByHvName()

datapath-windows: add WCHAR version of OvsFindVportByHvName()

In this patch, we rename the existing OvsFindVportByHvName() to
OvsFindVportByHvNameA() to indicate that the input string is an ASCII
string. We also define a OvsFindVportByHvNameW() that takes as input a
WCHAR string.

This will be used later in HvCreatPort() to check for ports with
duplicate names.

Signed-off-by: Nithin Raju <nithin@vmware.com>
Acked-by: Ankur Sharma <ankursharma@vmware.com>
Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>