[PATCH] arm/arm64: smccc: Use xN for arm64 register constraints with clang

[Nick Desaulniers]

Note that a patch in this form has previously been implemented by:

Andrey Konovalov <andreyknvl at google.com>:
https://gist.github.com/xairy/ee11682ea86044a45c0291c528cd936f

and another by:

Greg Hackmann <ghackmann at google.com>:
https://android-review.googlesource.com/c/kernel/common/+/645181

If you used either as a reference, you may want to credit them with a
`Suggested-by:` in the commit message.

On Thu, Mar 22, 2018 at 2:28 PM Matthias Kaehlcke <mka at chromium.org> wrote:
> +#ifndef __clang__
> +#define __reg__ "r"
> +#else
> +#define __reg__ "x"
> +#endif

Can this be flipped to #ifdef __clang__ ?  having an if...else where the
conditional negated is kind of funny.

--
Thanks,
~Nick Desaulniers