Fix nios2 port WRT fallthru

[Jeff Law]

Inserts a suitable return rather than falling through.  Installing on 
the trunk.

Jeff
commit 7a2cc4bd5ebbc3133fa1c89320ca82bb4b3b4a71
Author: law <law@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Wed Oct 26 15:47:48 2016 +0000

        * config/nios2/nios2.c (nios2_rtx_costs): Avoid fallthru.
    
    git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@241566 
138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5214b9d..448aaa7 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,7 @@
 2016-10-26  Jeff Law  <l...@redhat.com>
 
+       * config/nios2/nios2.c (nios2_rtx_costs): Avoid fallthru.
+
        * config/rl78/rl78.c (rl78_calculate_death_notes): Add fallthru
        comment.
        (rl78_asm_ctor_dtor): Increase buffer size.
diff --git a/gcc/config/nios2/nios2.c b/gcc/config/nios2/nios2.c
index 8afb468..2a28fad 100644
--- a/gcc/config/nios2/nios2.c
+++ b/gcc/config/nios2/nios2.c
@@ -1493,6 +1493,7 @@ nios2_rtx_costs (rtx x, machine_mode mode 
ATTRIBUTE_UNUSED,
           *total = COSTS_N_INSNS (1);
           return true;
        }
+      return false;
 
       default:
         return false;