drm: convert drm_atomic_uapi.c to new debug helpers

Migrate from DRM_DEBUG_ATOMIC to drm_dbg_atomic.

Signed-off-by: Simon Ser <contact@emersion.fr>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/FpVdsmqIh7IkH7YIwBjmp5ict1qi4NZlwHrIps@cp4-web-034.plabs.ch