USB: serial: digi_acceleport: fix write buffer corruption

In the Linux kernel, the following vulnerability has been resolved: USB: serial: digi_acceleport: fix write buffer corruption The digi_write_inb_command() is supposed to wait for the write urb to become available or return an error, but instead it updates the transfer buffer and tries to resubmit the urb on timeout. To make things worse, for commands like break control where no timeout is used, the driver would corrupt the urb immediately due to a broken jiffies comparison (on 32-bit machines this takes five minutes of uptime to trigger due to INITIAL_JIFFIES). Fix this by adding the missing return on timeout and waiting indefinitely when no timeout has been specified as intended. This issue was (sort of) flagged by Sashiko when reviewing an unrelated change to the driver.