(sched_analyze_2): Remove an explicit dependence between an insn that uses CC0 and the immediately previous insn.

(sched_analyze_2): Remove an explicit dependence between an insn
that uses CC0 and the immediately previous insn.
(SCHED_GROUP_P represents the dependence.)
(schedule_block): Only check sets_cc0_p on an insn.

From-SVN: r2010