tc: f_u32: fix json object leak

tc: f_u32: fix json object leak

Previously, the code returned directly within the switch statement in
the functions print_{ipv4, ipv6}. While this approach was functional,
after the commit 721435dc, we can no longer return directly because we
need to close the match object. To resolve this issue, replace the return
statement with break.

Fixes: 721435dcfd92 ("tc: u32: add json support in `print_raw`, `print_ipv4`, `print_ipv6`")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>