MachineFunctionProperties/MIRParser: Rename AllVRegsAllocated->NoVRegs, compute it

MachineFunctionProperties/MIRParser: Rename AllVRegsAllocated->NoVRegs, compute it

Rename AllVRegsAllocated to NoVRegs. This avoids the connotation of
running after register and simply describes that no vregs are used in
a machine function. With that we can simply compute the property and do
not need to dump/parse it in .mir files.

Differential Revision: http://reviews.llvm.org/D23850

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279698 91177308-0d34-0410-b5e6-96231b3b80d8