arch-arm: Add missing template declaration

The lack of a template declaration for IllegalInstSetStateFault was
causing errors when compiling with clang.

Change-Id: If7f19d7e879330226c80df2baca73d88d818f673
Signed-off-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/14618
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
diff --git a/src/arch/arm/faults.hh b/src/arch/arm/faults.hh
index dcda03b..859fd34 100644
--- a/src/arch/arm/faults.hh
+++ b/src/arch/arm/faults.hh
@@ -612,6 +612,7 @@
 template<> ArmFault::FaultVals ArmFaultVals<VirtualInterrupt>::vals;
 template<> ArmFault::FaultVals ArmFaultVals<FastInterrupt>::vals;
 template<> ArmFault::FaultVals ArmFaultVals<VirtualFastInterrupt>::vals;
+template<> ArmFault::FaultVals ArmFaultVals<IllegalInstSetStateFault>::vals;
 template<> ArmFault::FaultVals ArmFaultVals<SupervisorTrap>::vals;
 template<> ArmFault::FaultVals ArmFaultVals<SecureMonitorTrap>::vals;
 template<> ArmFault::FaultVals ArmFaultVals<PCAlignmentFault>::vals;