selftests/bpf: Fix endianness issue in __qspinlock declaration

Copy the big-endian field declarations from qspinlock_types.h,
otherwise some properties won't hold on big-endian systems. For
example, assigning lock->val = 1 should result in lock->locked == 1,
which is not the case there.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20250424165525.154403-4-iii@linux.ibm.com


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