v6.5 backport request: 6d2779ecaeb56f92 ("locking/atomic: scripts: fix fallback ifdeffery")

Hi,

Could we please backport commit:

6d2779ecaeb56f92d7105c56772346c71c88c278 ("locking/atomic: scripts: fix fallback ifdeffery")

... to the 6.5.y stable tree?

I forgot to Cc stable when I submitted the original patch, and had (mistakenly) assumed that the Fixes tag was sufficient.

The patch fixes a dentry cache corruption issue observed on arm64 and which is in theory possible on other architectures. I've recevied an off-list report from someone who's hit the issue on the v6.5.y tree specifically.

Thanks, Mark