lavc/flacdsp: R-V V LPC32

The entire set of 32 coefficients and corresponding past 32 samples can
fit in a single vector (with LMUL=8) exactly, but... since widening
double the needed vector sizes, we still end up too short with 128-bit
vectors. This adds a very simple version for future 256+-bit hardware,
and for pred_orders values up to 16, and a bit more involved loop for
for 128-bit hardware with pred_orders between 17 and 32.

With 128-bit hardware, the benchmarks look like this:
flac_lpc_32_13_c:       30152.0
flac_lpc_32_13_rvv_i32: 10244.7
flac_lpc_32_16_c:       37314.2
flac_lpc_32_16_rvv_i32: 10126.2
flac_lpc_32_29_c:       61910.0
flac_lpc_32_29_rvv_i32: 14495.2
flac_lpc_32_32_c:       68204.0
flac_lpc_32_32_rvv_i32: 13273.7

0 files changed, 0 insertions, 0 deletions