freedreno/ir3: add dummy bary.f(ei) for pre-fs-fetch

freedreno/ir3: add dummy bary.f(ei) for pre-fs-fetch

If the only use of varyings is a pre-shader texture-fetch, we still need
to issue a bary.f with the end-input flag, otherwise we'll block further
VS invocations, as the hw will think varying storage is still busy.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>