drm: mali-dp: Refactor plane initialisation

As we add more features, it makes sense to skip all the features not
supported by the smart layer together, instead of checking each one
individually. Achieve this by refactoring the plane init loop.

Signed-off-by: Brian Starkey <brian.starkey@arm.com>
[re-factor code after upstream changed rotation property to be per-plane]
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>