Fix comment spelling {addresing -> addressing} (NFC)

Author: mmalcomson

llvm/lib/Target/ARM/ARMISelLowering.h

@@ -377,7 +377,7 @@ class VectorType;
 
     bool isLegalT2ScaledAddressingMode(const AddrMode &AM, EVT VT) const;
 
-    /// Returns true if the addresing mode representing by AM is legal
+    /// Returns true if the addressing mode representing by AM is legal
     /// for the Thumb1 target, for a load/store of the specified type.
     bool isLegalT1ScaledAddressingMode(const AddrMode &AM, EVT VT) const;