sata_rcar: Add compatible string for r8a7795

R-Car H3 SoC has compatible SATA controller with R-Car Gen2 SoCs.

Signed-off-by: Kouei Abe <kouei.abe.cp@renesas.com>
Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Simon Horman <horms+renesas@verge.net.au>