ata: sata_rcar: drop useless initializer

There is no need to initialize the variable ret.

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>