[RegisterBankInfo] Simplify the API for build a register bank.
As part of the TRI argument of addRegBankCoverage we already have access to
the TargetRegisterClass through the ID of that register class.
Therefore, there is no point in needing a TargetRegisterClass instance,
the ID is enough to get to it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265487 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed