USB: serial: remove driver version information

Remove all MODULE_VERSION macros and driver-version information (except
for garmin_gps which uses it in a status reply).

It is the kernel version that matters and not some private version
scheme which rarely even gets updated.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>