selftests/bpf: by default use arch mask allowing all archs

If test case does not specify architecture via __arch_* macro consider
that it should be run for all architectures.

Fixes: 7d743e4c ("selftests/bpf: __jited test tag to check disassembly after jit")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20240822084112.3257995-6-eddyz87@gmail.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>