USB: cypress_m8: allow unstable baud rates

I've got a crappy cypress converter here, and while running at higher
baud rates craps out on throughput, it works fine with lower ones.
While it'd be nice to simply use a lower baud rate, not all devices
can be configured this way, and it is possible to (slowly) interact
at higher rates by sending a byte at a time.  So let people force
higher rates when they need it via a module parameter.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>