devicetree: fix newly added exynos sata bindings

Commit ba0d7ed3

 "ARM: dts: enable ahci sata and sata phy for
exynos5250" added a new binding document for the sata phy device,
and changed the sata controller binding. However, in both cases
significant aspects of the binding remained undocumented.
This attempts to reconstruct the actual binding from the usage.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Yuvaraj Kumar C D <yuvaraj.cd@samsung.com>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Kukjin Kim <kgene.kim@samsung.com>