[AMDGPU] Simplify definition of AddrSpaces. NFC. (llvm#141030)

Author: jayfoad

llvm/lib/Target/AMDGPU/AMDGPUInstructions.td

@@ -11,7 +11,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-class AddressSpacesImpl {
+def AddrSpaces {
   int Flat = 0;
   int Global = 1;
   int Region = 2;
@@ -21,8 +21,6 @@ class AddressSpacesImpl {
   int Constant32Bit = 6;
 }
 
-def AddrSpaces : AddressSpacesImpl;
-
 
 class AMDGPUInst <dag outs, dag ins, string asm = "",
   list<dag> pattern = []> : Instruction {