Fix typos in selftest/bpf files

Run spell checker on files in selftest/bpf and fixed typos.

Signed-off-by: Taichi Nishimura <awkrail01@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/bpf/20230216085537.519062-1-awkrail01@gmail.com