b43legacy: fix a lower bounds test

stable inclusion
from stable-5.10.80
commit 508faf8721aea6b67a9e7d77b772f8649080c4f4
bugzilla: 185821 https://gitee.com/openeuler/kernel/issues/I4L7CG

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=508faf8721aea6b67a9e7d77b772f8649080c4f4

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

[ Upstream commit c1c8380b ]

The problem is that "channel" is an unsigned int, when it's less 5 the
value of "channel - 5" is not a negative number as one would expect but
is very high positive value instead.

This means that "start" becomes a very high positive value.  The result
of that is that we never enter the "for (i = start; i <= end; i++) {"
loop.  Instead of storing the result from b43legacy_radio_aci_detect()
it just uses zero.

Fixes: 75388acd ("[B43LEGACY]: add mac80211-based driver for legacy BCM43xx devices")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NMichael Büsch <m@bues.ch>
Signed-off-by: NKalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211006073542.GD8404@kiliSigned-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Reviewed-by: NWeilong Chen <chenweilong@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/net/wireless/broadcom/b43legacy/radio.c

@@ -283,7 +283,7 @@ u8 b43legacy_radio_aci_scan(struct b43legacy_wldev *dev)
 			    & 0x7FFF);
 	b43legacy_set_all_gains(dev, 3, 8, 1);
 
-	start = (channel - 5 > 0) ? channel - 5 : 1;
+	start = (channel > 5) ? channel - 5 : 1;
 	end = (channel + 5 < 14) ? channel + 5 : 13;
 
 	for (i = start; i <= end; i++) {