selftests/bpf: rename test_tc_edt.bpf.c section to expose program type

selftests/bpf: rename test_tc_edt.bpf.c section to expose program type

The test_tc_edt BPF program uses a custom section name, which works fine
when manually loading it with tc, but prevents it from being loaded with
libbpf.

Update the program section name to "tc" to be able to manipulate it with
a libbpf-based C test.

Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
Link: https://lore.kernel.org/r/20251128-tc_edt-v2-1-26db48373e73@bootlin.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>