drm/i915: WARN in case we're enabling the pipe and it's enabled
... and QUIRK_PIPEA_FORCE is not present.
I initially thought that case was impossible and just added a WARN on
it, but then I was told this case is possible due to
QUIRK_PIPEA_FORCE. So let's add a WARN that serves two purposes:
- tell us in case we have done something wrong;
- document the only case where we expect this.
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com> Reviewed-by: Damien Lespiau <damien.lespiau@intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>