S/390: Remove superfluous commutative constraint modifiers

S/390: Remove superfluous commutative constraint modifiers

For operands with an identical set of alternatives there is no point
in marking them commutative.  This patch removes the superfluous
constraint modifiers in vector.md and vx-builtins.md since it might
slow down reload without buying us anything.

There were even two patterns where the constraint modifier was plain
wrong: "sub<VF_HW>3" and "ior_not<VT>3". Fortunately it never had any effect.

gcc/ChangeLog:

2020-04-02  Andreas Krebbel  <krebbel@linux.ibm.com>

	* config/s390/vector.md ("<ti*>add<mode>3", "mul<mode>3")
	("and<mode>3", "notand<mode>3", "ior<mode>3", "ior_not<mode>3")
	("xor<mode>3", "notxor<mode>3", "smin<mode>3", "smax<mode>3")
	("umin<mode>3", "umax<mode>3", "vec_widen_smult_even_<mode>")
	("vec_widen_umult_even_<mode>", "vec_widen_smult_odd_<mode>")
	("vec_widen_umult_odd_<mode>", "add<mode>3", "sub<mode>3")
	("mul<mode>3", "fma<mode>4", "fms<mode>4", "neg_fma<mode>4")
	("neg_fms<mode>4", "*smax<mode>3_vxe", "*smaxv2df3_vx")
	("*smin<mode>3_vxe", "*sminv2df3_vx"): Remove % constraint
	modifier.
	("vec_widen_umult_lo_<mode>", "vec_widen_umult_hi_<mode>")
	("vec_widen_smult_lo_<mode>", "vec_widen_smult_hi_<mode>"):
	Remove constraints from expander.
	* config/s390/vx-builtins.md ("vacc<bhfgq>_<mode>", "vacq")
	("vacccq", "vec_avg<mode>", "vec_avgu<mode>", "vec_vmal<mode>")
	("vec_vmah<mode>", "vec_vmalh<mode>", "vec_vmae<mode>")
	("vec_vmale<mode>", "vec_vmao<mode>", "vec_vmalo<mode>")
	("vec_smulh<mode>", "vec_umulh<mode>", "vec_nor<mode>3")
	("vfmin<mode>", "vfmax<mode>"): Remove % constraint modifier.