bpf: Don't allocate per-cpu extra_elems for fd htab

The update of element in fd htab is in-place now, therefore, there is no
need to allocate per-cpu extra_elems, just remove it.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250401062250.543403-6-houtao@huaweicloud.com


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