USB: serial: ch341: fix lost character on LCR updates

USB: serial: ch341: fix lost character on LCR updates

commit 62d1b60030ecef48209e7b7687641c04d7a40771 upstream.

Disable LCR updates for pre-0x30 devices which use a different (unknown)
protocol for line control and where the current register write causes
the next received character to be lost.

Note that updating LCR using the INIT command has no effect on these
devices either.

Reported-by: Jonathan Woithe <jwoithe@just42.net>
Tested-by: Jonathan Woithe <jwoithe@just42.net>
Link: https://lore.kernel.org/r/Ys1iPTfiZRWj2gXs@marvin.atrad.com.au
Fixes: ddd74a622bf0 ("USB: serial: ch341: reinitialize chip on reconfiguration")
Fixes: c73dfc7221e8 ("USB: serial: ch341: fix baud rate and line-control handling")
Cc: stable@vger.kernel.org      # 4.10
Signed-off-by: Johan Hovold <johan@kernel.org>
[ johan: adjust context to 5.4 ]
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>