rsi: use macro for allocating USB buffer

4 bytes is fixed size for reading or writing USB register. We
will use a macro instead of hardcoding this.

Fixes: b97e9b94ad ("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

@@ -162,7 +162,7 @@ static int rsi_usb_reg_read(struct usb_device *usbdev,
 	u8 *buf;
 	int status = -ENOMEM;
 
-	buf  = kmalloc(0x04, GFP_KERNEL);
+	buf  = kmalloc(RSI_USB_CTRL_BUF_SIZE, GFP_KERNEL);
 	if (!buf)
 		return status;
 
@@ -204,7 +204,7 @@ static int rsi_usb_reg_write(struct usb_device *usbdev,
 	u8 *usb_reg_buf;
 	int status = -ENOMEM;
 
-	usb_reg_buf  = kmalloc(0x04, GFP_KERNEL);
+	usb_reg_buf  = kmalloc(RSI_USB_CTRL_BUF_SIZE, GFP_KERNEL);
 	if (!usb_reg_buf)
 		return status;
 

drivers/net/wireless/rsi/rsi_usb.h

@@ -37,6 +37,7 @@
 #define BT_EP                        2
 
 #define RSI_USB_BUF_SIZE	     4096
+#define RSI_USB_CTRL_BUF_SIZE	     0x04
 
 struct rsi_91x_usbdev {
 	struct rsi_thread rx_thread;