[ARM] Add curly braces around switch case [NFC]

[peter.smith]

Summary

My previous commit r304702 introduced a new case into a switch statement. This case defined a variable but I forgot to add the curly brackets around the case to limit the scope.

This change puts the curly braces back in so that the next person that adds a case doesn't get a build failure. Thanks to avieira for the spot.

[avieira]

LGTM, thanks for the patch!

lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp

unsigned ARMAsmBackend::adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
   }
   case ARM::fixup_arm_mod_imm:
     Value = ARM_AM::getSOImmVal(Value);
     if (Value >> 12) {
       Ctx.reportError(Fixup.getLoc(), "out of range immediate fixup value");
       return 0;
     }
     return Value;
-  case ARM::fixup_t2_so_imm:
+  case ARM::fixup_t2_so_imm: {
     Value = ARM_AM::getT2SOImmVal(Value);
     if ((int64_t)Value < 0) {
       Ctx.reportError(Fixup.getLoc(), "out of range immediate fixup value");
       return 0;
     }
     // Value will contain a 12-bit value broken up into a 4-bit shift in bits
     // 11:8 and the 8-bit immediate in 0:7. The instruction has the immediate
     // in 0:7. The 4-bit shift is split up into i:imm3 where i is placed at bit
     // 10 of the upper half-word and imm3 is placed at 14:12 of the lower
     // half-word.
     uint64_t EncValue = 0;
     EncValue |= (Value & 0x800) << 15;
     EncValue |= (Value & 0x700) << 4;
     EncValue |= (Value & 0xff);
     return swapHalfWords(EncValue, IsLittleEndian);
   }
   }
+}
 
 void ARMAsmBackend::processFixupValue(const MCAssembler &Asm,
                                       const MCAsmLayout &Layout,
                                       const MCFixup &Fixup,
                                       const MCFragment *DF,
                                       const MCValue &Target, uint64_t &Value,
                                       bool &IsResolved) {
   const MCSymbolRefExpr *A = Target.getSymA();