drm: fix some kernel-doc markups

Some identifiers have different names between their prototypes
and the kernel-doc markup.

Others need to be fixed, as kernel-doc markups should use this format:
        identifier - description

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/12d4ca26f6843618200529ce5445063734d38c04.1605521731.git.mchehab+huawei@kernel.org