drivers: serial: jsm: Enable support for Digi Classic adapters

This commit enables support for the Digi Classic adapters line in the
jsm driver. This means changes in:
	- device probing code
	- device cleanup code
	- driver description (Kconfig)

The init/cleanup code is based on the staging/dgnc driver.

Signed-off-by: Konrad Zapalowicz <bergo.torino@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>