ARM: Move declaration of supportSplitCSR to be public (llvm#144679)

This is an implementation of a public method from the base
class, so it should also be public. Avoids unrelated diff
in a future patch.

Author: arsenm

llvm/lib/Target/ARM/ARMISelLowering.h

@@ -716,6 +716,11 @@ class VectorType;
       return true;
     }
 
+    bool supportSplitCSR(MachineFunction *MF) const override {
+      return MF->getFunction().getCallingConv() == CallingConv::CXX_FAST_TLS &&
+             MF->getFunction().hasFnAttribute(Attribute::NoUnwind);
+    }
+
     bool hasStandaloneRem(EVT VT) const override {
       return HasStandaloneRem;
     }
@@ -914,11 +919,6 @@ class VectorType;
                             SmallVectorImpl<SDValue> &InVals, bool isThisReturn,
                             SDValue ThisVal, bool isCmseNSCall) const;
 
-    bool supportSplitCSR(MachineFunction *MF) const override {
-      return MF->getFunction().getCallingConv() == CallingConv::CXX_FAST_TLS &&
-          MF->getFunction().hasFnAttribute(Attribute::NoUnwind);
-    }
-
     void initializeSplitCSR(MachineBasicBlock *Entry) const override;
     void insertCopiesSplitCSR(
       MachineBasicBlock *Entry,