sgiioc4: use ide_host_add() (take 2)

Convert the driver to use ide_host_add() -- this seems to be a straightforward
change which I'm not sure why hasn't been done yet...

While doing this at last, get rid of:

- useless local copy of the 'sgiioc4_port_info' variable;

- unnecessary 'goto' and label...

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: jeremy@sgi.com
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>