Port more assembler tests over to disassembler tests, and fix a minor logic error that exposed.

llvm-svn: 139240
diff --git a/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp b/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
index cd0e5e4..3b4e1c5 100644
--- a/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
+++ b/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
@@ -2786,7 +2786,7 @@
         break;
       case 0xf3bf8f6:
         Inst.setOpcode(ARM::t2ISB);
-        return MCDisassembler::Success;
+        break;
     }
 
     unsigned imm = fieldFromInstruction32(Insn, 0, 4);