[TargetLowering] Use StringRef::split instead of SplitString. NFC

SplitString splits based on a list of delimeters, but we're only using one delimeter so we should use the simpler split.

llvm-svn: 331613
diff --git a/llvm/lib/CodeGen/TargetLoweringBase.cpp b/llvm/lib/CodeGen/TargetLoweringBase.cpp
index beeff7d..e18a6ab 100644
--- a/llvm/lib/CodeGen/TargetLoweringBase.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringBase.cpp
@@ -1723,7 +1723,7 @@
     return TargetLoweringBase::ReciprocalEstimate::Unspecified;
 
   SmallVector<StringRef, 4> OverrideVector;
-  SplitString(Override, OverrideVector, ",");
+  Override.split(OverrideVector, ',');
   unsigned NumArgs = OverrideVector.size();
 
   // Check if "all", "none", or "default" was specified.
@@ -1783,7 +1783,7 @@
     return TargetLoweringBase::ReciprocalEstimate::Unspecified;
 
   SmallVector<StringRef, 4> OverrideVector;
-  SplitString(Override, OverrideVector, ",");
+  Override.split(OverrideVector, ',');
   unsigned NumArgs = OverrideVector.size();
 
   // Check if "all", "default", or "none" was specified.