i915: Fix complete texturing regression since 27505a105a

I had notes to myself to test gen3 and gen4, and then I tested gen4
and called it good.  Turns out I forgot to actually call the new
function on gen3.

src/mesa/drivers/dri/i915/i915_context.c

@@ -164,6 +164,8 @@ i915CreateContext(int api,
       return false;
    }
 
+   intel_init_texture_formats(ctx);
+
    _math_matrix_ctr(&intel->ViewportMatrix);
 
    /* Initialize swrast, tnl driver tables: */