Mark the neon intrinsics as inline(always).

[JamieCunliffe]

Mark the neon intrinics as inline(always) now that we can apply the attribute at the call site and perform the checks to ensure that inlining would be correct. See tracking issue rust-lang/rust#145574 for more info.

This will trigger some warnings on code that is using intrinsics without having enabled the correct target feature in the function they are being called from.