selftests/powerpc: unmark non-kernel-doc comments

Drop the 'beginning of kernel-doc' notation markers (/**)
in places that are not in kernel-doc format.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210325200820.16594-1-rdunlap@infradead.org