[PATCH] dri2: Fix authentication for < v8 clients (v2).

[Knut Petersen]

:
> The legacy logic was embarassingly wrong; AuthMagic should return errno,
> so returning FALSE only when AuthMagic returns nonzero is exactly wrong.
>
> v2: Match drmAuthMagic by returning -EINVAL rather than EINVAL
>      Fix trailing whitespace

ACK.

Tested-by: Knut Petersen <knut_petersen at t-online.de>