Fix PR3241: Currently EmitCopyFromReg emits a copy from the physical register...

Fix PR3241: Currently EmitCopyFromReg emits a copy from the physical register to a virtual register unless it requires an expensive cross class copy. That means we are only treating "expensive to copy" register dependency as physical register dependency.
Also future proof the scheduler to handle "normal" physical register dependencies. The code is not exercised yet.

llvm-svn: 62074