arm64: dts: ensure backward compatibility of the AP807 Xenon

A recent switch to a dedicated AP807 compatible string for the Xenon
SD/MMC controller result in the driver not being probed when
using updated device tree with the older kernel revisions.
It may also be problematic for other OSs/firmware that use
Linux device tree sources as a reference. Resolve the problem
with backward compatibility by restoring a previous compatible
string as secondary one.

Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>