Don't require pseudo-instructions to carry encoding information.

Don't require pseudo-instructions to carry encoding information.

For now this is distinct from isCodeGenOnly, as code-gen-only
instructions can (and often do) still have encoding information
associated with them. Once we've migrated all of them over to true
pseudo-instructions that are lowered to real instructions prior to
the printer/emitter, we can remove isCodeGenOnly and just use isPseudo.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134539 91177308-0d34-0410-b5e6-96231b3b80d8