Replaced two instances of std::function with auto.

Thanks to Zachary Turner for the suggestion.  It's distasteful that the actual
type of the lambda can't be spelled out, but it should be evident from the
definition of the lambda body.

llvm-svn: 281536
diff --git a/lldb/source/Target/StackFrame.cpp b/lldb/source/Target/StackFrame.cpp
index eb49724..570464b 100644
--- a/lldb/source/Target/StackFrame.cpp
+++ b/lldb/source/Target/StackFrame.cpp
@@ -1608,10 +1608,9 @@
     }
 
     Instruction::Operand *origin_operand = nullptr;
-    std::function<bool(const Instruction::Operand &)> clobbered_reg_matcher =
-        [reg_info](const Instruction::Operand &op) {
-          return MatchRegOp(*reg_info)(op) && op.m_clobbered;
-        };
+    auto clobbered_reg_matcher = [reg_info](const Instruction::Operand &op) {
+      return MatchRegOp(*reg_info)(op) && op.m_clobbered;
+    };
 
     if (clobbered_reg_matcher(operands[0])) {
       origin_operand = &operands[1];