USB: serial: sierra driver debug info visibility improvement

- Version number set to 1.3.5
 - Added "\n" at the end of each string in dev_dbg() code to improve the debug
   information visibility. Without this change the debug logs are very
   difficult to read.

Signed-off-by: Elina Pasheva <epasheva@sierrawireless.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>