AMDGPU: Set CopyCost of register classes
AMDGPU: Set CopyCost of register classes

These require multiple mov instructions to copy,
but the default value is that 1 instruction is needed.
I'm not sure if this actually changes anything.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@248651 91177308-0d34-0410-b5e6-96231b3b80d8

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