ARM: mach-shmobile: r8a7779: add SATA support

Add SATA clock for r8a7779 SoC (for both device tree and usual cases).
Register SATA controller as a "late" platform device on r8a7779 SoC.

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>