sfc: ef10: Fix assigning negative value to unsigned variable

stable inclusion
from stable-v5.10.121
commit 005990e30d14b1d70eceaaf712c413046be3b2d6
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5L6CQ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=005990e30d14b1d70eceaaf712c413046be3b2d6

--------------------------------

[ Upstream commit b8ff3395 ]

fix warning reported by smatch:
251 drivers/net/ethernet/sfc/ef10.c:2259 efx_ef10_tx_tso_desc()
warn: assigning (-208) to unsigned variable 'ip_tot_len'
Signed-off-by: NHaowen Bai <baihaowen@meizu.com>
Acked-by: NEdward Cree <ecree.xilinx@gmail.com>
Link: https://lore.kernel.org/r/1649640757-30041-1-git-send-email-baihaowen@meizu.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

drivers/net/ethernet/sfc/ef10.c

@@ -2240,7 +2240,7 @@ int efx_ef10_tx_tso_desc(struct efx_tx_queue *tx_queue, struct sk_buff *skb,
 	 * guaranteed to satisfy the second as we only attempt TSO if
 	 * inner_network_header <= 208.
 	 */
-	ip_tot_len = -EFX_TSO2_MAX_HDRLEN;
+	ip_tot_len = 0x10000 - EFX_TSO2_MAX_HDRLEN;
 	EFX_WARN_ON_ONCE_PARANOID(mss + EFX_TSO2_MAX_HDRLEN +
 				  (tcp->doff << 2u) > ip_tot_len);