qemu-option: Pull out "Supported options" print

It really is up to the caller to decide what this list of options means.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NJohn Snow <jsnow@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-id: 20180509210023.20283-4-mreitz@redhat.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>

qemu-img.c

@@ -260,6 +260,7 @@ static int print_block_option_help(const char *filename, const char *fmt)
         create_opts = qemu_opts_append(create_opts, proto_drv->create_opts);
     }
 
+    printf("Supported options:\n");
     qemu_opts_print_help(create_opts);
     qemu_opts_free(create_opts);
     return 0;

util/qemu-option.c

@@ -220,7 +220,6 @@ void qemu_opts_print_help(QemuOptsList *list)
 
     assert(list);
     desc = list->desc;
-    printf("Supported options:\n");
     while (desc && desc->name) {
         printf("%-16s %s\n", desc->name,
                desc->help ? desc->help : "No description available");