[mlir] Use StringRef::consume_front (NFC) (#139459)

diff --git a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
index ad4f65d..1168b9f 100644
--- a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
@@ -296,8 +296,7 @@
       return failure();
   }
   StringRef layoutSpec(llvmDataLayout);
-  if (layoutSpec.starts_with("-"))
-    layoutSpec = layoutSpec.drop_front();
+  layoutSpec.consume_front("-");
 
   return llvm::DataLayout(layoutSpec);
 }