IB/hfi1: Adjust fd->entry_to_rb allocation type

IB/hfi1: Adjust fd->entry_to_rb 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 "struct tid_rb_node **", but the return type will be
"struct rb_node **". These are the same allocation size (pointer size),
but the types do not match. Adjust the allocation type to match the
assignment.

Signed-off-by: Kees Cook <kees@kernel.org>
Link: https://patch.msgid.link/20250426061247.work.261-kees@kernel.org
Signed-off-by: Leon Romanovsky <leon@kernel.org>