USB: serial: ch341: change initial line-control settings

commit 7c61b0d5 upstream.

Some CH340 devices appear unable to change the initial LCR settings, so
set a sane 8N1 default during probe to enable basic support for such
devices.

Also drop a redundant LCR read during device initialisation.

Signed-off-by: Johan Hovold <johan@kernel.org>