[VPlan] Get type from start value for VPWidenIntOrFpInduction (NFC).

NFC for now but this can cause verification failures in the future,
since after bf5627c85e697 wide induction may be narrowed. By using the
type from the start value, we will always return the correct type.

llvm/lib/Transforms/Vectorize/VPlan.h

diff --git a/llvm/lib/Transforms/Vectorize/VPlan.h b/llvm/lib/Transforms/Vectorize/VPlan.h
index 5fd7a36..5bc012c 100644
--- a/llvm/lib/Transforms/Vectorize/VPlan.h
+++ b/llvm/lib/Transforms/Vectorize/VPlan.h
@@ -2004,7 +2004,8 @@
 
   /// Returns the scalar type of the induction.
   Type *getScalarType() const {
-    return Trunc ? Trunc->getType() : getPHINode()->getType();
+    return Trunc ? Trunc->getType()
+                 : getStartValue()->getLiveInIRValue()->getType();
   }
 
   /// Returns the VPValue representing the value of this induction at