drm: mali-dp: switch to drm_*_get(), drm_*_put() helpers

Use drm_*_get() and drm_*_put() helpers instead of drm_*_reference()
and drm_*_unreference() helpers.

drm_*_reference() and drm_*_unreference() functions are just
compatibility alias for drm_*_get() and drm_*_put() and should not be
used by new code. So convert all users of compatibility functions to
use the new APIs.

Generated by: scripts/coccinelle/api/drm-get-put.cocci

Signed-off-by: Cihangir Akturk <cakturk@gmail.com>
Acked-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>