ptp: ocp: Add const to bp->attr_group allocation type

In preparation for making the kmalloc family of allocators type aware,
we need to make sure that the returned type from the allocation matches
the type of the variable being assigned. (Before, the allocator would
always return "void *", which can be implicitly cast to any pointer type.)

The assigned type is "const struct attribute_group **", but the returned
type, while technically matching, will be not const qualified. As there is
no general way to safely add const qualifiers, adjust the allocation type
to match the assignment.

Signed-off-by: Kees Cook <kees@kernel.org>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20250426061858.work.470-kees@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>