ARM: mach-shmobile: r8a7779: SATA DT configuration

Allow configuration of the r8a7779 SoC SATA controller using a flattened device
tree.

Signed-off-by: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>