dev: Don't fall through into BRAR after RFDR case

If the switch block inside the RFDR case selects the non-default case
and breaks out, it will fall through into the BRAR case, which seems
incorrect.  Put in a break to ensure that it breaks out of the parent
switch block as well.

Change-Id: Ie4cedf66954b7e8f4b884ad9e3a653968bbfaef7
Signed-off-by: Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com>
Reviewed-on: https://gem5-review.googlesource.com/8563
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

src/dev/net/ns_gige.cc

@@ -742,6 +742,7 @@ NSGigE::write(PacketPtr pkt)
                 panic("writing RFDR for something other than pattern matching "
                     "or hashing! %#x\n", rfaddr);
             }
+            break;
 
           case BRAR:
             regs.brar = reg;