Improve selection of short instruction for fp-moves.

gcc/
2018-05-17  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/arc.md (movsf_insn): Add short instruction selection.
	* config/arc/constraints.md (CfZ): New constraint.
	* config/arc/fpu.md (addssf3_fpu): Use CfZ constraint.
	(subsf3_fpu): Likewise.
	(cmpsf_fpu): Likewise.
	(cmpsf_fpu_uneq): Likewise.

From-SVN: r262971