freedreno: use SAMPLE_COUNT to autotune sysmem vs gmem
Rough idea, if we can recognize sequences of render passes (perhaps by framebuffer state and maybe approx # of draws?), we could use sample count delta from start/end of batch.. and use that make better choice about gmem vs sysmem on the next frame.
Presumably something like this will be easier with vk since the render-passes are explicit.