[Thumb/Thumb2] Added restrictions on PC, LR, SP in the register list for PUSH/POP/LDM/STM. <Differential Revision: http://reviews.llvm.org/D6090>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223356 91177308-0d34-0410-b5e6-96231b3b80d8