pata_ns87415: define SUPERIO_IDE_MAX_RETRIES

Code copied from drivers/ide/pci/ns87415.c uses this, so copy the
definition from there as well.

Fixes the following build error:
  CC [M]  drivers/ata/pata_ns87415.o
drivers/ata/pata_ns87415.c: In function ‘ns87560_read_buggy’:
drivers/ata/pata_ns87415.c:228: error: ‘SUPERIO_IDE_MAX_RETRIES’ undeclared (first use in this function)
drivers/ata/pata_ns87415.c:228: error: (Each undeclared identifier is reported only once
drivers/ata/pata_ns87415.c:228: error: for each function it appears in.)

Signed-off-by: Frank Lichtenheld <frank@lichtenheld.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>