This patch is pretty similar to the VECREDUCE_ADD patch, with some minor tweaks.
- Results from the AArch64ISD::[SMAX|SMIN]V_PRED return element sized results. This requires an ANY_EXTEND for results < 32-bits, since Legalization promotes those results. (*Unless I misunderstood something*)
- There is no NEON i64 vector support for SMAXV|SMINV, so use SVE for those.