etnaviv: Supertiled texture support on gc3000

etnaviv: Supertiled texture support on gc3000

Support supertiled textures on hardware that has the appropriate
feature flag SUPERTILED_TEXTURE.

Most of the scaffolding was already in place in etna_layout_multiple:

   case ETNA_LAYOUT_SUPER_TILED:
      *paddingX = 64;
      *paddingY = 64;
      *halign = TEXTURE_HALIGN_SUPER_TILED;

So this is just a matter of allowing it.

Signed-off-by: Wladimir J. van der Laan <laanwj@gmail.com>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>