[MIPS] Migrate reduction optabs in mips-ps-3d.md

[MIPS] Migrate reduction optabs in mips-ps-3d.md

	* config/mips/mips-ps-3d.md (reduc_splus_v2sf): Remove.
	(reduc_plus_scal_v2sf): New.
	(reduc_smax_v2sf): Rename to...
	(reduc_smax_scal_v2sf): ...here, make result SFmode, add vec_extract.
	(reduc_smin_v2sf): Rename to...
	(reduc_smin_scal_v2sf): ...here, make result SFmode, add vec_extract.

From-SVN: r232371