tty: moxa: merge moxa.h into moxa.c

There is no need for existence of a separate header for Moxa's Intellio
cards. Merge it into moxa.c to clean up the tty dir a bit.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210914090823.17206-1-jslaby@suse.cz


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