vc4: Claim the GL 2.1 minimum for 3D textures.

We don't actually do them (or even fake them) currently, but it does get
us a bunch of unrelated glean glsl1 tests passing, which previously would
error out due to glean assuming the minimums on a 3D texture that 2 of the
subtests use.

src/gallium/drivers/vc4/vc4_screen.c

@@ -176,7 +176,8 @@ vc4_screen_get_param(struct pipe_screen *pscreen, enum pipe_cap param)
         case PIPE_CAP_MAX_TEXTURE_CUBE_LEVELS:
                 return VC4_MAX_MIP_LEVELS;
         case PIPE_CAP_MAX_TEXTURE_3D_LEVELS:
-                return 1;
+                /* Note: Not supported in hardware, just faking it. */
+                return 5;
         case PIPE_CAP_MAX_TEXTURE_ARRAY_LAYERS:
                 return 0;