sata_rcar: fix deferred probing

The driver overrides the error codes returned by platform_get_irq() to
-EINVAL, so if it returns -EPROBE_DEFER, the driver would fail the probe
permanently instead of the deferred probing. Switch to propagating the
error code upstream, still checking/overriding IRQ0 as libata regards it
as "no IRQ" (thus polling) anyway...

Fixes: 9ec36caf

 ("of/irq: do irq resolution in platform_get_irq")
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>