staging: wfx: fix case where RTS threshold is 0

If RTS threshold is 0, it currently disables RTS. It should mean
"enabled for every frames".
Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200115135338.14374-44-Jerome.Pouiller@silabs.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wfx/hif_tx_mib.h

@@ -391,7 +391,7 @@ static inline int hif_wep_default_key_id(struct wfx_vif *wvif, int val)
 static inline int hif_rts_threshold(struct wfx_vif *wvif, int val)
 {
 	struct hif_mib_dot11_rts_threshold arg = {
-		.threshold = cpu_to_le32(val > 0 ? val : 0xFFFF),
+		.threshold = cpu_to_le32(val >= 0 ? val : 0xFFFF),
 	};
 
 	return hif_write_mib(wvif->wdev, wvif->id,