[CostModel][X86] Fixed AVX1/AVX512 sdiv/udiv general costs for 256/512 bit integer vectors

We weren't accounting for legal types on every subtarget, meaning that many of the costs were using defaults.

We still don't correctly cost (or test) the 512-bit sdiv/udiv by uniform const cases, nor the power-of-2 cases.

llvm-svn: 284744