ephysics - fix stacking comparsion correctly if 1 smaller than 1

this fixes a pretty trivial comparison issue..

found by PVS studio

@fix

src/lib/ephysics/ephysics_body.cpp

@@ -447,7 +447,7 @@ _ephysics_body_evas_stacking_sort_cb(const void *d1, const void *d2)
    if (!stacking2) return -1;
 
    if (stacking1->stacking < stacking2->stacking) return -1;
-   if (stacking2->stacking > stacking2->stacking) return 1;
+   if (stacking1->stacking > stacking1->stacking) return 1;
 
    return 0;
 }