nvk: Don't use a descriptor cbuf if it's too large
This fixes a test on vkd3d-proton commit 836446ce25 VKD3D_TEST_FILTER=test_typed_buffers_many_objects_dxil build/tests/d3d12 Fixes: f1c909ed ("nvk/nir: Add cbuf analysis to nvi_nir_lower_descriptors()") Part-of: <mesa/mesa!28844> (cherry picked from commit 6b22fff6)