AMDGPU/GlobalISel: Address post-commit review comments for r332379

MCRegisterInfo::getPhysRegSize() will be deprecated.

llvm-svn: 332856
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp b/llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp
index 3d255a8c..5f2436b 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp
@@ -224,7 +224,7 @@
   } else {
     const TargetRegisterClass *RC = TRI.getRegClassForReg(MRI, DstReg);
     IsSgpr = TRI.isSGPRClass(RC);
-    Size = RC->MC->getPhysRegSize() * 8;
+    Size = TRI.getRegSizeInBits(*RC);
   }
 
   if (Size != 32 && Size != 64)