ARM: dts: r8a7779: Remove deprecated "renesas, rcar-sata" compatible value

The "renesas,rcar-sata" compatible value was deprecated by
"renesas,sata-r8a7779" many years ago, in commit e67adb4e
("sata_rcar: Add R-Car Gen2 SATA PHY support").  Drop it.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/20200219153929.11073-1-geert+renesas@glider.be