ARM: Permit "sp" in ARM variant of STREXD instructions

Patch from Mihail Popa

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179854 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/Disassembler/ARMDisassembler.cpp b/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
index 631168b..32b47fb 100644
--- a/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
+++ b/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
@@ -3573,7 +3573,7 @@
   unsigned Rn = fieldFromInstruction(Insn, 16, 4);
   unsigned pred = fieldFromInstruction(Insn, 28, 4);
 
-  if (!Check(S, DecoderGPRRegisterClass(Inst, Rd, Address, Decoder)))
+  if (!Check(S, DecodeGPRnopcRegisterClass(Inst, Rd, Address, Decoder)))
     return MCDisassembler::Fail;
 
   if ((Rt & 1) || Rt == 0xE || Rn == 0xF) return MCDisassembler::Fail;