svga: check TXF instruction's target to determine MSAA

Rather than the currently bound texture.  This goes along with the
earlier patch to get away from examining bound textures and sampler
views during shader translation.

Fixes VMware bug 1632739.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>

src/gallium/drivers/svga/svga_tgsi_vgpu10.c

@@ -5439,7 +5439,7 @@ emit_txf(struct svga_shader_emitter_v10 *emit,
          const struct tgsi_full_instruction *inst)
 {
    const uint unit = inst->Src[1].Register.Index;
-   const unsigned msaa = emit->key.tex[unit].texture_msaa;
+   const boolean msaa = tgsi_is_msaa_target(inst->Texture.Texture);
    int offsets[3];
    struct tex_swizzle_info swz_info;