Move spill size and alignment info from MC to TargetRegisterInfo

Move spill size and alignment info from MC to TargetRegisterInfo

This is another step towards implementing register classes with
parametrized register/spill sizes and value types.

This is an updated version of r298652. The difference is that MCRegister-
Class still contains register size, available as getPhysRegSize(). The
old function getSize was retained as a temporary measure to avoid build
breakage for out-of-tree targets.

llvm-svn: 298739