it's more elegant to put the "getConstantPool" and

it's more elegant to put the "getConstantPool" and
"getFixedStack" on the MachinePointerInfo class.  While
this isn't the problem I'm setting out to solve, it is the
right way to eliminate PseudoSourceValue, so lets go with it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@114406 91177308-0d34-0410-b5e6-96231b3b80d8