locking/arch: Avoid variable shadowing in local_try_cmpxchg()

Several architectures define arch_try_local_cmpxchg macro using
internal temporary variables named ___old, __old or _old. Remove
temporary varible in local_try_cmpxchg to avoid variable shadowing.

No functional change intended.

Fixes: d994f2c8 ("locking/arch: Wire up local_try_cmpxchg()")
Closes: https://lore.kernel.org/lkml/CAFGhKbyxtuk=LoW-E3yLXgcmR93m+Dfo5-u9oQA_YC5Fcy_t9g@mail.gmail.com/


Reported-by: Charlemagne Lasse <charlemagnelasse@gmail.com>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230708090048.63046-1-ubizjak@gmail.com