drm/arm/komeda: update DMA mask to 40 bits

Each layer in the DPU has a 40-bit base address register, which indicates
start of frame buffer data for that layer. Komeda driver does not set
its DMA mask, which makes it 32-bit by default which does not use
the entire available possible supported by the DPU.

Update the DMA mask to align with DPU Architecture v1.0 spec.

Signed-off-by: Amjad Ouled-Ameur <amjad.ouled-ameur@arm.com>
Signed-off-by: Faiz Abbas <faiz.abbas@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240219100915.192475-4-faiz.abbas@arm.com
Acked-by: Liviu Dudau <liviu.dudau@arm.com>