fix(morello): dts: use documented DPU compatible string

The official Arm Komeda DPU DT binding only mentions the "arm,mali-d71"
string as a possible compatible string. The D32 version is just a
variant of the D71, and the revision can and will be auto-detected at
runtime.
Add the usual fallback compatible string scheme to contain a documented
compatible string.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Change-Id: Ic1eade122b030dc983944b161eec175facf75357
1 file changed