radeonsi/gfx9: use CE RAM optimally

radeonsi/gfx9: use CE RAM optimally

On GFX9 with only 4K CE RAM, define the range of slots that will be
allocated in CE RAM. All other slots will be uploaded directly. This will
switch dynamically according to which slots are used by current shaders.

GFX9 CE usage should now be similar to VI instead of being often disabled.

Tested on VI by taking the GFX9 CE allocation codepath and setting
num_ce_slots = 2 everywhere to get frequent switches between both modes.
CE is still disabled on GFX9.

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>