serial: 8250_pnp: Simplify "line" related code

serial: 8250_pnp: Simplify "line" related code

8250_pnp sets drvdata to line + 1 if the probe is successful. The users
of drvdata are in remove, suspend and resume callbacks, none of which
will be called if probe failed. The line acquired from drvdata can
never be zero in those functions and the checks for that can be
removed.

Eliminate also +/-1 step because all users of line subtract 1 from the
value.

These might have been leftover from legacy PM callbacks that could
be called without probe being successful.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20240506121202.11253-1-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>