Change one more atomic size in detect.h

Change uint16_t to int for better tile atomic performance. Checked with
pahole that it doesn't increase the size of the structure.

src/detect.h

@@ -800,7 +800,7 @@ typedef struct DetectionEngineThreadCtx_ {
     /** ID of the transaction currently being inspected. */
     uint64_t tx_id;
 
-    SC_ATOMIC_DECLARE(uint16_t, so_far_used_by_detect);
+    SC_ATOMIC_DECLARE(int, so_far_used_by_detect);
 
     /* holds the current recursion depth on content inspection */
     int inspection_recursion_counter;