Remove scalable vector assert from InnerLoopVectorizer::setDebugLocFromInst

In InnerLoopVectorizer::setDebugLocFromInst we were previously
asserting that the VF is not scalable. This is because we want to
use the number of elements to create a duplication factor for the
debug profiling data. However, for scalable vectors we only know the
minimum number of elements. I've simply removed the assert for now
and added a FIXME saying that we assume vscale is always 1. When
vscale is not 1 it just means that the profiling data isn't as
accurate, but shouldn't cause any functional problems.

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -1052,7 +1052,7 @@ void InnerLoopVectorizer::setDebugLocFromInst(IRBuilder<> &B, const Value *Ptr)
     // factors to the discriminators.
     if (DIL && Inst->getFunction()->isDebugInfoForProfiling() &&
         !isa<DbgInfoIntrinsic>(Inst) && !EnableFSDiscriminator) {
-      assert(!VF.isScalable() && "scalable vectors not yet supported.");
+      // FIXME: For scalable vectors, assume vscale=1.
       auto NewDIL =
           DIL->cloneByMultiplyingDuplicationFactor(UF * VF.getKnownMinValue());
       if (NewDIL)