arch-arm: Corrected encoding for T32 HVC instruction

This patch corrects the encoding of the HVC (Hypervisor Call) for the
T32 instruction set.

Change-Id: I6f77eaf5c586697e9ccd588419c61e6d90c6c7bf
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Chuan Zhu <chuan.zhu@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/5541
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

src/arch/arm/isa/formats/branch.isa

@@ -1,6 +1,6 @@
 // -*- mode:c++ -*-
 
-// Copyright (c) 2010, 2012-2013 ARM Limited
+// Copyright (c) 2010,2012-2013,2017 ARM Limited
 // All rights reserved
 //
 // The license below extends only to copyright in the software and shall
@@ -247,7 +247,7 @@ def format Thumb32BranchesAndMiscCtrl() {{
                             }
                         }
                     }
-                  case 0xfe:
+                  case 0x7e:
                     {
                         uint32_t imm16 = (bits(machInst, 19, 16) << 12) |
                                          (bits(machInst, 11,  0) <<  0);