turnip: consider multiview_mask when clearing depth-stencil attachment

Otherwise only first layer is being cleared. Because only fb->layers count of layers would be cleared and layers == 1 for multiview case:

width, height and layers define the dimensions of the framebuffer. If the render pass uses multiview, then layers must be one and each attachment requires a number of layers that is greater than the maximum bit index set in the view mask in the subpasses in which it is used.

Would fix several VK_EXT_multi_draw tests:

 dEQP-VK.draw.multi_draw.overlapping.normal.max_draws.*.vert_only.multiview.no_offset