glsl: Fix subscripted arrays with no XFB packing

We need to duplicate the subscripted members even if they happen to be
aligned, since the other elements may be passed into the consumer
shader. Fixes on Panfrost:

dEQP-GLES3.functional.transform_feedback.array_element.interleaved.lines.highp_float

Note: the test did pass on main previously due to an elaborate set of
driver hacks. I don't believe the old behaviour was correct regardless.

Only Panfrost is affected by this change and the next, as every other
driver sets PIPE_CAP_PACKED_STREAM_OUTPUT.

Acked-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10778>

src/compiler/glsl/link_varyings.h

@@ -130,9 +130,9 @@ public:
       return !this->next_buffer_separator && !this->skip_components;
    }
 
-   bool is_aligned(unsigned dmul, unsigned offset) const
+   bool subscripted() const
    {
-      return (dmul * (this->array_subscript + offset)) % 4 == 0;
+      return this->is_subscripted;
    }
 
    const char *name() const