tty: cyclades, fix nports handling

Set up ports right after FW load so that we won't allocate maximal
(64) ports when we use few.

Also remove reading of nports in irq context, since we know it from
initialisation now.

This also fixes a tty ports unregistration on some fail paths and for
Ze which registered 64 and unregistered real port count.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>