Arm: Add NEON and MVE RTL patterns for Complex Addition.

Arm: Add NEON and MVE RTL patterns for Complex Addition.

This adds implementation for the optabs for complex additions.  With this the
following C code:

  void f90 (float complex a[restrict N], float complex b[restrict N],
	    float complex c[restrict N])
  {
    for (int i=0; i < N; i++)
      c[i] = a[i] + (b[i] * I);
  }

generates

  f90:
	  add     r3, r2, #1600
  .L2:
	  vld1.32 {q8}, [r0]!
	  vld1.32 {q9}, [r1]!
	  vcadd.f32       q8, q8, q9, #90
	  vst1.32 {q8}, [r2]!
	  cmp     r3, r2
	  bne     .L2
	  bx      lr

instead of

  f90:
	  add     r3, r2, #1600
  .L2:
	  vld2.32 {d24-d27}, [r0]!
	  vld2.32 {d20-d23}, [r1]!
	  vsub.f32	q8, q12, q11
	  vadd.f32	q9, q13, q10
	  vst2.32 {d16-d19}, [r2]!
	  cmp     r3, r2
	  bne     .L2
	  bx      lr

gcc/ChangeLog:

	* config/arm/arm_mve.h (__arm_vcaddq_rot90_u8, __arm_vcaddq_rot270_u8,
	__arm_vcaddq_rot90_s8, __arm_vcaddq_rot270_s8,
	__arm_vcaddq_rot90_u16, __arm_vcaddq_rot270_u16,
	__arm_vcaddq_rot90_s16, __arm_vcaddq_rot270_s16,
	__arm_vcaddq_rot90_u32, __arm_vcaddq_rot270_u32,
	__arm_vcaddq_rot90_s32, __arm_vcaddq_rot270_s32,
	__arm_vcaddq_rot90_f16, __arm_vcaddq_rot270_f16,
	__arm_vcaddq_rot90_f32, __arm_vcaddq_rot270_f32):  Update builtin calls.
	* config/arm/arm_mve_builtins.def (vcaddq_rot90_u, vcaddq_rot270_u,
	vcaddq_rot90_s, vcaddq_rot270_s, vcaddq_rot90_f, vcaddq_rot270_f):
	Removed.
	(vcaddq_rot90, vcaddq_rot270): New.
	* config/arm/constraints.md (Dz): Include MVE.
	* config/arm/iterators.md (mve_rot): New.
	(supf): Remove VCADDQ_ROT270_S, VCADDQ_ROT270_U, VCADDQ_ROT90_S,
	VCADDQ_ROT90_U.
	(VCADDQ_ROT270, VCADDQ_ROT90): Removed.
	* config/arm/mve.md (mve_vcaddq_rot270_<supf><mode,
	mve_vcaddq_rot90_<supf><mode>, mve_vcaddq_rot270_f<mode>,
	mve_vcaddq_rot90_f<mode>): Removed.
	(mve_vcaddq<mve_rot><mode>, mve_vcaddq<mve_rot><mode>): New.
	* config/arm/unspecs.md (VCADDQ_ROT270_S, VCADDQ_ROT90_S,
	VCADDQ_ROT270_U, VCADDQ_ROT90_U, VCADDQ_ROT270_F,
	VCADDQ_ROT90_F): Removed.
	* config/arm/vec-common.md (cadd<rot><mode>3): New.