[clang] [llvm] [RISCV][P-ext] Support Packed Multiplication with Widening Horizontal Addition intrinsics (PR #232612)

[Craig Topper via cfe-commits]

topperc wrote:

I pushed merge because I changed widenPackedVectorWithZeros to generate pack instead of zext.w recently in #232940.

https://github.com/llvm/llvm-project/pull/232612