target/riscv: rvv: Handle source overlap of vector widening reduction instructions

Widening reductions read vs2 as a vector of SEW elements and vs1[0] as a scalar of 2*SEW. The ISA does not allow the same vector register to be read with different EEWs, so they must not overlap. vs1 is read as a scalar from element 0, so it is treated as a single vector register (independent of LMUL) when checking overlap. Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3208 Signed-off-by: Anton Blanchard <antonb@tenstorrent.com> Acked-by: Alistair Francis <alistair.francis@wdc.com> Message-ID: <20260417080328.31918-1-antonb@tenstorrent.com> Signed-off-by: Alistair Francis <alistair.francis@wdc.com>