Char: mxser, remove predefined isa support

Remove a support of ISA addresses predefined at compile time.  It is
unused (filled by zeroes) and prolongs the code.  Don't initialize global
array and add `ioaddr' module param description.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>