bpf: Check KF_bpf_rbtree_add_impl for the "case KF_ARG_PTR_TO_RB_NODE"

bpf: Check KF_bpf_rbtree_add_impl for the "case KF_ARG_PTR_TO_RB_NODE"

In a later patch, two new kfuncs will take the bpf_rb_node pointer arg.

struct bpf_rb_node *bpf_rbtree_left(struct bpf_rb_root *root,
				    struct bpf_rb_node *node);
struct bpf_rb_node *bpf_rbtree_right(struct bpf_rb_root *root,
				     struct bpf_rb_node *node);

In the check_kfunc_call, there is a "case KF_ARG_PTR_TO_RB_NODE"
to check if the reg->type should be an allocated pointer or should be
a non_owning_ref.

The later patch will need to ensure that the bpf_rb_node pointer passing
to the new bpf_rbtree_{left,right} must be a non_owning_ref. This
should be the same requirement as the existing bpf_rbtree_remove.

This patch swaps the current "if else" statement. Instead of checking
the bpf_rbtree_remove, it checks the bpf_rbtree_add. Then the new
bpf_rbtree_{left,right} will fall into the "else" case to make
the later patch simpler. bpf_rbtree_add should be the only
one that needs an allocated pointer.

This should be a no-op change considering there are only two kfunc(s)
taking bpf_rb_node pointer arg, rbtree_add and rbtree_remove.

Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20250506015857.817950-2-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>