i965: Remove remaining uses of ctx->Const.UniformBooleanTrue in visitors

i965: Remove remaining uses of ctx->Const.UniformBooleanTrue in visitors

Since commit 2881b123, we have used 0/~0 for representing booleans on all
gens.  However, we still had a bunch of places in the visitor code where we
were still referring to ctx->Const.UniformBooleanTrue.  Since this is
always ~0, we can just remove them.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>