PerfectCacheMemory: Add return statements to two functions.

Two functions in src/mem/ruby/system/PerfectCacheMemory.hh, tryCacheAccess()
and cacheProbe(), end with calls to panic(). Both of these functions have
return type other than void. Any file that includes this header file fails
to compile because of the missing return statement. This patch adds dummy
values so as to avoid the compiler warnings.

src/mem/ruby/system/PerfectCacheMemory.hh

@@ -124,6 +124,7 @@ PerfectCacheMemory<ENTRY>::tryCacheAccess(const CacheMsg& msg,
                                           bool& block_stc, ENTRY*& entry)
 {
     panic("not implemented");
+    return true;
 }
 
 // tests to see if an address is present in the cache
@@ -167,6 +168,7 @@ inline Address
 PerfectCacheMemory<ENTRY>::cacheProbe(const Address& newAddress) const
 {
     panic("cacheProbe called in perfect cache");
+    return newAddress;
 }
 
 // looks an address up in the cache