ARM: fix thumb coprocessor instruction with pre-writeback disassembly

was        stc2 p0, c0, [r0]!
instead of stc2 p0, c0, [r0,#0]!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@183975 91177308-0d34-0410-b5e6-96231b3b80d8