datapath-windows: Update netlink family IDs

I didn't realize earlier while defining OvsDpInterfaceExt.h that
there are special values defined in netlink-protocol.h for nlmsg_type.
For Eg. NLMSG_ERROR is defined to be 2. In this patch, we update the
values of the family IDs to not clash with the special defines.
I'm using NLMSG_MIN_TYPE as a reference.

All this points to doing family ID lookup from the kernel rather than
returning values from netlink-socket.c. We should move to that model
after we get through the first round of netlink commands.

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