Use designated initializers for struct msghdr.
The struct layout is non-portable and musl libc does not match what busybox expects.
Signed-off-by: Szabolcs Nagy <nsz@port70.net>
Tested-by: Waldemar Brodkorb <wbx@openadk.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>