This increases the group multiplier as per T-Head C910 benchmarks:

inverse_coupling_c: 4597.0
inverse_coupling_rvv_i32: 1312.7 (m1)
inverse_coupling_rvv_i32: 1116.7 (m2)
inverse_coupling_rvv_i32: 732.2  (m4)
inverse_coupling_rvv_i32: 898.0  (m8)