Revert "selftests/bpf: dummy_st_ops should reject 0 for non-nullable params"

This reverts commit e7d19307 which is
commit 6a2d30d3 upstream.

The dummy_st_ops/dummy_sleepable_reject_null test requires commit 980ca8ce
("bpf: check bpf_dummy_struct_ops program params for test runs"), which in turn
depends on "Support PTR_MAYBE_NULL for struct_ops arguments" series (see link
below), neither are backported to stable 6.6.

Link: https://lore.kernel.org/all/20240209023750.1153905-1-thinker.li@gmail.com/


Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>