wifi: ath9k: fix parameter check in ath9k_init_debug()

Make IS_ERR() judge the debugfs_create_dir() function return
in ath9k_init_debug()
Signed-off-by: Minjie Du <duminjie@vivo.com>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230712114740.13226-1-duminjie@vivo.com

drivers/net/wireless/ath/ath9k/debug.c

@@ -1420,7 +1420,7 @@ int ath9k_init_debug(struct ath_hw *ah)
 
 	sc->debug.debugfs_phy = debugfs_create_dir("ath9k",
 						   sc->hw->wiphy->debugfsdir);
-	if (!sc->debug.debugfs_phy)
+	if (IS_ERR(sc->debug.debugfs_phy))
 		return -ENOMEM;
 
 #ifdef CONFIG_ATH_DEBUG