[llvm] Changed default value of slp-max-vf to 192 (PR #70479)

[Dmitriy Smirnov via llvm-commits]

d-smirnov wrote:

@alexey-bataev, @vporpo  Looks like I narrowed down "search space" a bit. The demonstrator IR is attached.
[full.ll.gz](https://github.com/llvm/llvm-project/files/13323659/full.ll.gz)
`/usr/bin/time opt --passes="loop-vectorize,sroa,simplifycfg,slp-vectorizer" full.ll --disable-output --pass-remarks=slp-vectorize`
Run takes about 30 minutes on Graviton 3 machine with unlimited chains and 13 sec with --slp-max-vf=192
Most of the time spent slp-vectorizing `compute_uwshcu` subroutine 

https://github.com/llvm/llvm-project/pull/70479