[ARM] Add registers to debuginfo MIR test cases.

Summary:
MIRParserImpl::computeFunctionProperties uses MRI.getNumVirtRegs() to
set the NoVReg property. By adding a bunch of registers to the MIR test
cases, the NoVReg property is not set when importing the MIR. Otherwise
NoVReg is set after instruction selection while the machine instructions
still contain virtual registers, causing expensive checks to fail.

Reviewers: efriedma, MatzeB, aprantl

Reviewed By: MatzeB, aprantl

Subscribers: aemerson, javed.absar, kristof.beyls, llvm-commits

Differential Revision: https://reviews.llvm.org/D36152

llvm-svn: 310178