Add support for the following Telit LE910Cx composition:

0x1250: rmnet, tty, tty, tty, tty
Reviewed-by: Daniele Palmas <dnlplm@gmail.com>
Signed-off-by: Carlo Lobrano <c.lobrano@gmail.com>
Link: https://lore.kernel.org/r/20220614075623.2392607-1-c.lobrano@gmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>