exynos4: Fix libfimc build

* Expected return type is an address, not a boolean.

Change-Id: I454c23b66388fe06fc6d630b7b510ae85bd94c4a

exynos4/hal/libfimc/SecFimc.cpp

@@ -751,7 +751,7 @@ SecBuffer * SecFimc::getMemAddr(int index)
 {
     if (mFlagCreate == false) {
         ALOGE("%s::Not yet created", __func__);
-        return false;
+        return NULL;
     }
 
     return &mDstBuffer[index];