fix: round position for vr{add,sub}hn_{s,u}{16,32,64}

[Zvictoria]

ut: int64_t r[12]; int8x8_t a0 = vraddhn_s16(vdupq_n_s16(1UL<< 7), vdupq_n_s16(0)); r[ 0] = vget_lane_s8 (a0, 0); int16x4_t a1 = vraddhn_s32(vdupq_n_s32(1UL<<15), vdupq_n_s32(0)); r[ 1] = vget_lane_s16(a1, 0); int32x2_t a2 = vraddhn_s64(vdupq_n_s64(1UL<<31), vdupq_n_s64(0)); r[ 2] = vget_lane_s32(a2, 0); uint8x8_t a3 = vraddhn_u16(vdupq_n_u16(1UL<< 7), vdupq_n_u16(0)); r[ 3] = vget_lane_u8 (a3, 0); uint16x4_t a4 = vraddhn_u32(vdupq_n_u32(1UL<<15), vdupq_n_u32(0)); r[ 4] = vget_lane_u16(a4, 0); uint32x2_t a5 = vraddhn_u64(vdupq_n_u64(1UL<<31), vdupq_n_u64(0)); r[ 5] = vget_lane_u32(a5, 0); int8x8_t s0 = vrsubhn_s16(vdupq_n_s16(1UL<< 7), vdupq_n_s16(0)); r[ 6] = vget_lane_s8 (s0, 0); int16x4_t s1 = vrsubhn_s32(vdupq_n_s32(1UL<<15), vdupq_n_s32(0)); r[ 7] = vget_lane_s16(s1, 0); int32x2_t s2 = vrsubhn_s64(vdupq_n_s64(1UL<<31), vdupq_n_s64(0)); r[ 8] = vget_lane_s32(s2, 0); uint8x8_t s3 = vrsubhn_u16(vdupq_n_u16(1UL<< 7), vdupq_n_u16(0)); r[ 9] = vget_lane_u8 (s3, 0); uint16x4_t s4 = vrsubhn_u32(vdupq_n_u32(1UL<<15), vdupq_n_u32(0)); r[10] = vget_lane_u16(s4, 0); uint32x2_t s5 = vrsubhn_u64(vdupq_n_u64(1UL<<31), vdupq_n_u64(0)); r[11] = vget_lane_u32(s5, 0); for(unsigned i = 0; i < 12; i++) { assert(r[i] == 1); }