freedreno/a6xx: Emit WFIs after CCU flushes
Fixes flakiness on dEQP-GLES3.functional.fbo.blit.depth_stencil.depth32f_stencil8* when the GPU is pinned to a higher frequency.
Fixes flakiness on dEQP-GLES3.functional.fbo.blit.depth_stencil.depth32f_stencil8* when the GPU is pinned to a higher frequency.