pal_idx_finish

Current benchmarks:

- Kendryte K230:
pal_idx_finish_w4_c:       123.6 ( 1.00x)
pal_idx_finish_w4_rvv:     122.5 ( 1.01x)
pal_idx_finish_w8_c:       303.6 ( 1.00x)
pal_idx_finish_w8_rvv:     213.1 ( 1.42x)
pal_idx_finish_w16_c:      869.4 ( 1.00x)
pal_idx_finish_w16_rvv:    474.0 ( 1.83x)
pal_idx_finish_w32_c:     1968.5 ( 1.00x)
pal_idx_finish_w32_rvv:    875.2 ( 2.25x)
pal_idx_finish_w64_c:     4741.1 ( 1.00x)
pal_idx_finish_w64_rvv:   1894.4 ( 2.50x)

- Banana Pi BPI-F3:
pal_idx_finish_w4_c:       122.4 ( 1.00x)
pal_idx_finish_w4_rvv:     141.4 ( 0.87x)
pal_idx_finish_w8_c:       289.3 ( 1.00x)
pal_idx_finish_w8_rvv:     211.7 ( 1.37x)
pal_idx_finish_w16_c:      788.2 ( 1.00x)
pal_idx_finish_w16_rvv:    458.8 ( 1.72x)
pal_idx_finish_w32_c:     1699.3 ( 1.00x)
pal_idx_finish_w32_rvv:    850.8 ( 2.00x)
pal_idx_finish_w64_c:     3978.9 ( 1.00x)
pal_idx_finish_w64_rvv:   1823.2 ( 2.18x)