pan/midgard: Implement textureOffset for 2D textures

Fixes dEQP-GLES3.functional.shaders.texture_functions.textureoffset.sampler2d_fixed_fragment.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3169>
9 files changed