Fix a bug with the ARM thumb2 CBNZ and CBNZ instructions that
branch to the next instruction.  This can not be encoded but can be
turned into a NOP.

rdar://15062072


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198904 91177308-0d34-0410-b5e6-96231b3b80d8