[PATCH v2] wifi: rtw88: usb: Simplify rtw_usb_write_data

[Bitterblue Smith <rtl8821cerfe2@xxxxxxxxx>]

The skb created in this function always has the same headroom,
the chip's TX descriptor size. (pkt_info->offset is set by
rtw_usb_write_data_rsvd_page() to chip->tx_pkt_desc_sz.) Use
chip->tx_pkt_desc_sz directly.

Signed-off-by: Bitterblue Smith <rtl8821cerfe2@xxxxxxxxx>
---
v2:
 - Don't touch rtw_usb_write_data_rsvd_page(). It needs to set
   pkt_info.offset after all, otherwise RTL8822BU and RTL8821CU fail
   to upload the firmware:

---
 drivers/net/wireless/realtek/rtw88/usb.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtw88/usb.c b/drivers/net/wireless/realtek/rtw88/usb.c
index 1dfe7c6ae4ba..a28f35a03b26 100644
--- a/drivers/net/wireless/realtek/rtw88/usb.c
+++ b/drivers/net/wireless/realtek/rtw88/usb.c
@@ -440,23 +440,21 @@ static int rtw_usb_write_data(struct rtw_dev *rtwdev,
 {
 	const struct rtw_chip_info *chip = rtwdev->chip;
 	struct sk_buff *skb;
-	unsigned int desclen, headsize, size;
+	unsigned int size;
 	u8 qsel;
 	int ret = 0;
 
 	size = pkt_info->tx_pkt_size;
 	qsel = pkt_info->qsel;
-	desclen = chip->tx_pkt_desc_sz;
-	headsize = pkt_info->offset ? pkt_info->offset : desclen;
 
-	skb = dev_alloc_skb(headsize + size);
+	skb = dev_alloc_skb(chip->tx_pkt_desc_sz + size);
 	if (unlikely(!skb))
 		return -ENOMEM;
 
-	skb_reserve(skb, headsize);
+	skb_reserve(skb, chip->tx_pkt_desc_sz);
 	skb_put_data(skb, buf, size);
-	skb_push(skb, headsize);
-	memset(skb->data, 0, headsize);
+	skb_push(skb, chip->tx_pkt_desc_sz);
+	memset(skb->data, 0, chip->tx_pkt_desc_sz);
 	rtw_tx_fill_tx_desc(pkt_info, skb);
 	rtw_tx_fill_txdesc_checksum(rtwdev, pkt_info, skb->data);
 
-- 
2.44.0