softpipe: Set samples and layers in set_framebuffer_state() cb

Carries across the number of samples and layers state in the
'softpipe_set_framebuffer_state()' callback. This state is
part of 'ARB_framebuffer_no_attachments' support.

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/gallium/drivers/softpipe/sp_state_surface.c

@@ -94,6 +94,8 @@ softpipe_set_framebuffer_state(struct pipe_context *pipe,
 
    sp->framebuffer.width = fb->width;
    sp->framebuffer.height = fb->height;
+   sp->framebuffer.samples = fb->samples;
+   sp->framebuffer.layers = fb->layers;
 
    sp->dirty |= SP_NEW_FRAMEBUFFER;
 }