[llvm] HexagonGenWideningVecInstr.cpp - fix MSVC "result of 32-bit shift implicitly converted to 64 bits" warning. NFC. (PR #171095)

[Fateme Hosseini via llvm-commits]

https://github.com/fhossein-quic approved this pull request.

Thanks for the fix

https://github.com/llvm/llvm-project/pull/171095