glsl: Drop do_common_optimization's max_unroll_iterations parameter.

glsl: Drop do_common_optimization's max_unroll_iterations parameter.

Now that we pass in gl_shader_compiler_options, it makes sense to just
use options->MaxUnrollIterations, rather than passing a separate
parameter.

Half of the invocations already passed options->MaxUnrollIterations,
while the other half passed in a hardcoded value of 32.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>