radv/gfx10: invalidate everything in L2 when shaders read data

radv/gfx10: invalidate everything in L2 when shaders read data

This includes metadata as well. On GFX10, we have to invalidate
the L2 metadata cache when shaders read DCC.

Note that we still have to implement GFX10 coherency by
introducing INV_L2_METATADA but for now just flush L2.

This fixes a corruption with DCC and Talos.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>