nvc0: increase number of ubo binding points

nvc0: increase number of ubo binding points

Apparently GL 4.5 requires 14 of these (there's a "*" in the spec, but
it's unclear what it refers to). We need to expose an extra binding
point for the "program parameters", which means this must be 15. Remove
the last vestige of the "use c14 for immediates" idea.

Fixes GL45-CTS.shading_language_420pack.binding_uniform_block_array

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