intel/compiler: Silence unused parameter warnings in empty vec4_instruction_scheduler...

intel/compiler: Silence unused parameter warnings in empty vec4_instruction_scheduler methods

src/intel/compiler/brw_schedule_instructions.cpp: In member function ‘virtual void vec4_instruction_scheduler::count_reads_remaining(backend_instruction*)’:
src/intel/compiler/brw_schedule_instructions.cpp:764:72: warning: unused parameter ‘be’ [-Wunused-parameter]
 vec4_instruction_scheduler::count_reads_remaining(backend_instruction *be)
                                                                        ^~
src/intel/compiler/brw_schedule_instructions.cpp: In member function ‘virtual void vec4_instruction_scheduler::setup_liveness(cfg_t*)’:
src/intel/compiler/brw_schedule_instructions.cpp:769:51: warning: unused parameter ‘cfg’ [-Wunused-parameter]
 vec4_instruction_scheduler::setup_liveness(cfg_t *cfg)
                                                   ^~~
src/intel/compiler/brw_schedule_instructions.cpp: In member function ‘virtual void vec4_instruction_scheduler::update_register_pressure(backend_instruction*)’:
src/intel/compiler/brw_schedule_instructions.cpp:774:75: warning: unused parameter ‘be’ [-Wunused-parameter]
 vec4_instruction_scheduler::update_register_pressure(backend_instruction *be)
                                                                           ^~
src/intel/compiler/brw_schedule_instructions.cpp: In member function ‘virtual int vec4_instruction_scheduler::get_register_pressure_benefit(backend_instruction*)’:
src/intel/compiler/brw_schedule_instructions.cpp:779:80: warning: unused parameter ‘be’ [-Wunused-parameter]
 vec4_instruction_scheduler::get_register_pressure_benefit(backend_instruction *be)
                                                                                ^~
src/intel/compiler/brw_schedule_instructions.cpp: In member function ‘virtual int vec4_instruction_scheduler::issue_time(backend_instruction*)’:
src/intel/compiler/brw_schedule_instructions.cpp:1550:61: warning: unused parameter ‘inst’ [-Wunused-parameter]
 vec4_instruction_scheduler::issue_time(backend_instruction *inst)
                                                             ^~~~

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>