Use individual register classes when spilling snippets.

Use individual register classes when spilling snippets.

The main register class may have been inflated by live range splitting, so that
register class is not necessarily valid for the snippet instructions.

Use the original register class for the stack slot interval.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128351 91177308-0d34-0410-b5e6-96231b3b80d8