[X86] Remove dead code for handling i8/i16 UMUL_LOHI/SMUL_LOHI from X86ISelDAGToDAG.cpp. NFC

These are promoted to i16/i32 multiplies by a DAG combine.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@329147 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed