rsi: fix static checker warning

u32 pointer is changed to u16 and filled the value. Problem is
solved by using local temporary variable. Below static checker
warning was reported.

drivers/net/wireless/rsi/rsi_91x_usb.c:400 rsi_usb_master_reg_read()
        warn: passing casted pointer 'value' to 'rsi_usb_reg_read()'
32 vs 16.

Fixes: b97e9b94ad75c ("rsi: Add new host interface operations")
Signed-off-by: Amitkumar Karwar <amit.karwar@redpinesignals.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/rsi/rsi_91x_usb.c

@@ -404,8 +404,15 @@ static int rsi_usb_master_reg_read(struct rsi_hw *adapter, u32 reg,
 {
 	struct usb_device *usbdev =
 		((struct rsi_91x_usbdev *)adapter->rsi_dev)->usbdev;
+	u16 temp;
+	int ret;
 
-	return rsi_usb_reg_read(usbdev, reg, (u16 *)value, len);
+	ret = rsi_usb_reg_read(usbdev, reg, &temp, len);
+	if (ret < 0)
+		return ret;
+	*value = temp;
+
+	return 0;
 }
 
 static int rsi_usb_master_reg_write(struct rsi_hw *adapter,