Fix handling of flag_rename_registers by a target.

Fix handling of flag_rename_registers by a target.

	PR target/102688

gcc/ChangeLog:

	* common.opt: Use EnabledBy instead of detection in
	finish_options and process_options.
	* opts.c (finish_options): Remove handling of
	x_flag_unroll_all_loops.
	* toplev.c (process_options): Likewise for flag_web and
	flag_rename_registers.