A single fix for the fallout of the recent futex uacess rework.

With those changes GCC9 fails to analyze arch_futex_atomic_op_inuser()
correctly and emits a 'maybe unitialized' warning. While we usually ignore
compiler stupidity the conditional store is pointless anyway because the
correct case has to store. For the fault case the extra store does no harm.
-----BEGIN PGP SIGNATURE-----
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=Va5K
-----END PGP SIGNATURE-----