server: Provide empty initialiser for struct option array

We see the following warning with certain compilers:

 console-server.c:460:2: error: missing initializer for field 'name' of 'const struct option' [-Werror=missing-field-initializers]
    { },

So use a proper empty initialiser here.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
diff --git a/console-server.c b/console-server.c
index 183d0ae..392b4a1 100644
--- a/console-server.c
+++ b/console-server.c
@@ -457,7 +457,7 @@
 }
 static const struct option options[] = {
 	{ "config",	required_argument,	0, 'c'},
-	{ },
+	{ 0 },
 };
 
 int main(int argc, char **argv)