bpf: Fix bpf_dynptr documentation comments

The function argument names were changed but the doc comment was not.
Fix htmldocs build warning by updating doc comments.

Fixes: cce4c40b ("bpf: treewide: Align kfunc signatures to prog point-of-view")
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Link: https://lore.kernel.org/r/d0b0eb05f91e12e5795966153b11998d3fc1d433.1718295425.git.dxu@dxuuu.xyz


Signed-off-by: Alexei Starovoitov <ast@kernel.org>