As in the aligned case, we can use VLSE64.V, though the way of doing so
gets more convoluted, so the performance gains are more modest:

get_pixels_unaligned_c:       126.7
get_pixels_unaligned_rvv_i32: 145.5 (before)
get_pixels_unaligned_rvv_i64:  62.2 (after)

For the reference, those are the aligned benchmarks (unchanged) on the
same T-Head C908 hardware:

get_pixels_c:                 126.7
get_pixels_rvi:                85.7
get_pixels_rvv_i64:            33.2