regrename: Don't rename the dest of a REG_CFA_REGISTER (PR85645)

regrename: Don't rename the dest of a REG_CFA_REGISTER (PR85645)

We should never change the destination of a REG_CFA_REGISTER, just
like for insns with a REG_CFA_RESTORE, because we need to have the
same control flow information on all branches that join.  It is very
doubtful that renaming the scratch registers used for prologue/epilogue
will help anything either.

	PR rtl-optimization/85645
	* regrename.c (build_def_use): Also kill the chains that include the
	destination of a REG_CFA_REGISTER note.

From-SVN: r260075