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

alac_append_extra_bits_mono_c: 803.0
alac_append_extra_bits_stereo_c: 1604.2
alac_decorrelate_stereo_c: 1077.5

LMUL=1
alac_append_extra_bits_mono_rvv_i32: 418.2
alac_append_extra_bits_stereo_rvv_i32: 693.2
alac_decorrelate_stereo_rvv_i32: 673.5

LMUL=2
alac_append_extra_bits_mono_rvv_i32: 382.2
alac_append_extra_bits_stereo_rvv_i32: 648.2
alac_decorrelate_stereo_rvv_i32: 542.7

LMUL=4
alac_append_extra_bits_mono_rvv_i32: 241.5
alac_append_extra_bits_stereo_rvv_i32: 512.7
alac_decorrelate_stereo_rvv_i32: 364.2

LMUL=8
alac_append_extra_bits_mono_rvv_i32: 239.7
alac_append_extra_bits_stereo_rvv_i32: 497.2
alac_decorrelate_stereo_rvv_i32: 426.7