bpf: Skip unit_size checking for global per-cpu allocator

bpf: Skip unit_size checking for global per-cpu allocator

For global per-cpu allocator, the size of free object in free list
doesn't match with unit_size and now there is no way to get the size of
per-cpu pointer saved in free object, so just skip the checking.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Closes: https://lore.kernel.org/bpf/20230913133436.0eeec4cb@canb.auug.org.au/
Signed-off-by: Hou Tao <houtao1@huawei.com>
Tested-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20230913135943.3137292-1-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>