drm: get rid of DRM_DEBUG_* log calls in drm core, files drm_a*.c

DRM_DEBUG_* and DRM_* log calls are deprecated.
Change them to drm_dbg_* / drm_{err,info,...} calls in drm core
files.

To avoid making a very big patch, this change is split in
smaller patches. This one includes drm_a*.c

Signed-off-by: Claudio Suarez <cssk@net-c.es>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/YaC7zXW119tlzfVh@gineta.localdomain