Originally I tried to fix where the nir itself has a shared mem size of 0,
but the frontend (here clover) set it to some value. But st/mesa presets
it on the state object and we actually double the value in the end.

Just use max the value and use the biggest one.

Fixes the compute_shader.shared-max CTS test.

Fixes: dc667b1f

 ("nv50/ir/nir: fix smem size")
Signed-off-by: Karol Herbst <kherbst@redhat.com>