dt-bindings: arm: Document SoC compatible value for Armadillo-800 EVA

The compatible property of the root node in a DTS for Atmark Techno
Armadillo-800 EVA should include the compatible value for the R-Mobile
A1 SoC, too.

Fixes: d2c2a077 ("ARM: shmobile: Add platform device tree bindings documentation")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>