sc16is7xx: Separate GPIOs from modem control lines

Export only the GPIOs that are not shared with hardware modem control
lines. Introduce new device parameter indicating whether modem control
lines are available.

Signed-off-by: Lech Perczak <l.perczak@camlintechnologies.com>
Signed-off-by: Tomasz Moń <tomasz.mon@camlingroup.com>
Link: https://lore.kernel.org/r/20220221105618.3503470-4-tomasz.mon@camlingroup.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>