pata_ipx4xx_cf: fix IRQ check

pata_ipx4xx_cf: fix IRQ check

The driver's probe() method is written as if platform_get_irq() returns 0
on error, while actually it returns a negative error code (with all the
other values considered valid IRQs).  Rewrite the driver's IRQ checking
code to pass the positive IRQ #s to ata_host_activate(), propagate errors
upstream, and treat IRQ0 as error, returning -EINVAL, as the libata code
treats 0  as  an indication that polling should be used anyway...

Fixes: 9dc1d3238181 ("[libata] ARM: add ixp4xx PATA driver")
Signed-off-by: Sergey Shtylyov <s.shtylyov@omprussia.ru>
Signed-off-by: Jens Axboe <axboe@kernel.dk>