Where pdx_subregs[regno] is used, reg_equiv[regno] is also used.

	* ira.c (pdx_subregs): Delete.
	(struct equivalence): Add pdx_subregs field.
	(set_paradoxical_subreg): Remove pdx_subregs param.  Update
	pdx_subregs access.
	(update_equiv_regs): Don't create or free pdx_subregs.  Update
	pdx_subregs access.

From-SVN: r235656