alpha: fix for no 'break' in the case statement

gem5 won't compile correctly since g++ will throw a warning (error)
that the next case statement below this one is reachable since there is
no 'break' statement.

Signed-off-by: Sujay Phadke

Change-Id: Icab646ee5abcfeb6ba3e690909042927b4003eba
Reviewed-on: https://gem5-review.googlesource.com/7521
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

src/arch/alpha/ev5.cc

diff --git a/src/arch/alpha/ev5.cc b/src/arch/alpha/ev5.cc
index 4d72104..ae8efa4 100644
--- a/src/arch/alpha/ev5.cc
+++ b/src/arch/alpha/ev5.cc
@@ -303,6 +303,7 @@
             if (tc->getKernelStats())
                 tc->getKernelStats()->mode(Kernel::kernel, tc);
         }
+        M5_FALLTHROUGH;
 
       case IPR_ICM:
         // only write two mode bits - processor mode