glsl: fix needs_lowering() call in varying packing pass

glsl: fix needs_lowering() call in varying packing pass

Here we remove the outer arrays on geom and tess shaders where
needed. Without this the pass can sometimes attempt to pack a
varying on only one side of the shader interface where it is not
actually needed. The result can be mismatching varying types.

Fixes: d6b9202873f0 ("glsl: disable varying packing when its not safe")

Tested-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Acked-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15761>