[GlobalISel] Mark newly-created gvregs as having a bank.

Also verify that we never try to set the size of a vreg associated
to a register class.

Report an error when we encounter that in MIR. Fix a testcase that
hit that error and had a size for no reason.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@276012 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed