serial: Use ARRAY_SIZE() with iso7816 reserved array

Instead of a literal, size the for loop iteration based on the actual
array using ARRAY_SIZE().

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230309080923.11778-2-ilpo.jarvinen@linux.intel.com


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