net: tun: Remove redundant assignment to ret

Variable 'ret' is set to zero but this value is never read as it is
overwritten with a new value later on, hence it is a redundant
assignment and can be removed.

Cleans up the following clang-analyzer warning:

drivers/net/tun.c:3008:2: warning: Value stored to 'ret' is never read
[clang-analyzer-deadcode.DeadStores]
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Link: https://lore.kernel.org/r/1619603852-114996-1-git-send-email-yang.lee@linux.alibaba.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/tun.c

@@ -3008,7 +3008,6 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
 		return open_related_ns(&net->ns, get_net_ns);
 	}
 
-	ret = 0;
 	rtnl_lock();
 
 	tun = tun_get(tfile);