bpf: Set and check spin lock value in sk_storage_map_test

bpf: Set and check spin lock value in sk_storage_map_test

Update sk_storage_map_test to make sure kernel does not copy user
non-zero value spin lock to kernel, and does not copy kernel spin
lock value to user.

If user spin lock value is copied to kernel, this test case will
make kernel spin on the copied lock, resulting in rcu stall and
softlockup.

Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Link: https://lore.kernel.org/r/20221114134720.1057939-3-xukuohai@huawei.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>