[X86] Move scheduling tests for CMPXCHG to the corresponding resources-x86_64.s files. NFC

In D66424 it has been requested to move all the new tests added by r369278 into
resources-x86_64.s. That is because only the 8b/16 ops should be tested by
resources-cmpxchg.s. This partially reverts r369278.

llvm-svn: 369288