tty/serial: Sort drivers in makefile

Sort drivers in alphabetic order in Makefile to make it easier to find
the correct line. In case the CONFIG and filenames disagree, sort using
the filename (but ignoring "serial" prefixes).

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230912103558.20123-1-ilpo.jarvinen@linux.intel.com


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