selftests/bpf: Test tail call counting with bpf2bpf and data on stack

selftests/bpf: Test tail call counting with bpf2bpf and data on stack

[ Upstream commit 5e0b0a4c52d30bb09659446f40b77a692361600d ]

Cover the case when tail call count needs to be passed from BPF function to
BPF function, and the caller has data on stack. Specifically when the size
of data allocated on BPF stack is not a multiple on 8.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220616162037.535469-3-jakub@cloudflare.com
Stable-dep-of: 96daa9874211 ("selftests/bpf: Correct map_fd to data_fd in tailcalls")
Signed-off-by: Sasha Levin <sashal@kernel.org>