[llvm-c][Disassembler] When printing latency information, skip scheduling
classes that are marked as Variant as those require an MI to pass to
SubTargetInfo::resolveSchedClass.

This is part of <rdar://problem/14687488>.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191864 91177308-0d34-0410-b5e6-96231b3b80d8