ata: sata_rcar: Remove unnecessary return value check

As commit ce753ad1 ("platform: finally disallow IRQ0 in
platform_get_irq() and its ilk") says, there is no need to
check if the platform_get_irq return value is 0. Let's remove it.

Signed-off-by: Yangtao Li <frank.li@vivo.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>