nvc0/ir: fix robustness guarantees for constbuf loads on kepler+ compute

nvc0/ir: fix robustness guarantees for constbuf loads on kepler+ compute

Kepler and up unfortunately only support up to 8 constbufs. We work
around this by loading from constbufs as if they were storage buffers.
However we were not consistently applying limits to loads from these
buffers. Make sure to do the same thing we do for storage buffers.

Fixes GL45-CTS.robust_buffer_access_behavior.uniform_buffer

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Cc: mesa-stable@lists.freedesktop.org