serial: sc16is7xx: Switch to use device_get_match_data()

Instead of open coded variants, switch to direct use of
device_get_match_data().

Tested-By: Georgii Staroselskii <georgii.staroselskii@emlid.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>