arch-arm: Fix fallthrough when trapping at EL2

This had been caused by the introduction of GICv3 registers trapping in
commit 32a23114c1

Change-Id: I5073e2891f3ff5c5a9e05d3456dad6f4f8ffba0d
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18909
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/arm/insts/misc64.cc

@@ -269,6 +269,7 @@ MiscRegOp64::checkEL2Trap(ThreadContext *tc, const MiscRegIndex misc_reg,
             break;
           case MISCREG_IMPDEF_UNIMPL:
             trap_to_hyp = hcr.tidcp && el == EL1;
+            break;
           // GICv3 regs
           case MISCREG_ICC_SGI0R_EL1:
             if (tc->getIsaPtr()->haveGICv3CpuIfc())