Fix MSVC unused variable warning. NFCI.

AMDGPURegisterInfo::getSubRegFromChannel is a static method - we don't need to get the AMDGPURegisterInfo instance.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@332807 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed