bridge: Deduplicate print_range()

bridge: Deduplicate print_range()

The two implementations are now identical so keep only one instance and
move it to json_print.c where there are already a few other specialized
printing functions.

The string that's formatted in the "end" buffer is only needed when
outputting a range so move the snprintf() call within the condition.

The second argument's purpose is better conveyed by calling it "end" rather
than "id" so rename it.

Reviewed-by: Petr Machata <petrm@nvidia.com>
Tested-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Benjamin Poirier <bpoirier@nvidia.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>