datapath-windows/Netlink: Added support for variable length attributes in validation.

Added minor fix for allowing support for variable lenghth attributes in
parsing policy.

Signed-off-by: Ankur Sharma <ankursharma@vmware.com>
Acked-by: Nithin Raju <nithin@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
datapath-windows: Add support for getting 64 and 16 bit attributes.

Signed-off-by: Ankur Sharma <ankursharma@vmware.com>
Acked-by: Nithin Raju <nithin@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
datapath-windows/Netlink: Add optional flag in policy.

Added the optional flag in policy structure. This would allow
caller to avoid checks for mandatory attributes if parsing
succeeds.

Signed-off-by: Ankur Sharma <ankursharma@vmware.com>
Acked-by: Nithin Raju <nithin@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>