openvswitch/types.h: Drop the member name in initializer macro

openvswitch/types.h: Drop the member name in initializer macro

MSVC++ compiler does not allow initializing a struct while
explicitly initializing a member in the struct.

Not allowed:
    static const struct eth_addr a = {{ .ea= { 0xff, 0xff, 0xff, 0xff,
                                        0xff, 0xff }}};

Alowed:
    static const struct eth_addr b  = {{{ 0xff, 0xff, 0xff, 0xff, 0xff,
                                          0xff }}};
*An extra curly brace is required for GCC in case the struct contains
a union.

Signed-off-by: Shashank Ram <rams@vmware.com>
Tested-by: Yi-Hung Wei <yihung.wei@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>