json_print: suppress clang format warning

json_print: suppress clang format warning

Clang complains about using non-format string in print_color_tv.

The ideal fix would be to put format attribute on all the print_XXX functions
in json_print.h. But that leads to furthur complications because the existing
code may pass a NULL as format if the format is unused since the print
is being done only for JSON output.

The comprimise is to just disable the warning for the one place
it shows up.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David Ahern <dsahern@kernel.org>