glsl: merge loop_controls.cpp with loop_unroll.cpp

Having this separate just makes the code harder to follow, and
requires an extra walk of the IR.

Reviewed-by: Thomas Helland <thomashelland90@gmail.com>

src/compiler/glsl/glsl_parser_extras.cpp

@@ -2216,7 +2216,6 @@ do_common_optimization(exec_list *ir, bool linked,
    if (options->MaxUnrollIterations) {
       loop_state *ls = analyze_loop_variables(ir);
       if (ls->loop_found) {
-         OPT(set_loop_controls, ir, ls);
          OPT(unroll_loops, ir, ls, options);
       }
       delete ls;