ARM instruction don't have instruction prefixes, so remove the helper functions for them from the MCCodeEmitter.
ARM instruction don't have instruction prefixes, so remove the helper functions
for them from the MCCodeEmitter.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@115975 91177308-0d34-0410-b5e6-96231b3b80d8

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