ath9k: debug: Remove redundant check

Variable val is unsigned, so checking whether it is less than zero is
redundant.
Signed-off-by: Christos Gkekas <chris.gekas@gmail.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

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

@@ -1167,7 +1167,7 @@ static ssize_t write_file_tpc(struct file *file, const char __user *user_buf,
 	if (kstrtoul(buf, 0, &val))
 		return -EINVAL;
 
-	if (val < 0 || val > 1)
+	if (val > 1)
 		return -EINVAL;
 
 	tpc_enabled = !!val;