USB: ftdi_sio: remove pointless syslog spew

Remove some pointless messages from the FTDI serial driver;
I found these filling up syslog on one system.  Also remove
a pointless "break" after a "return" in the same area.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>