drm/core: Use recommened kerneldoc for struct member refs

I just learned that &struct_name.member_name works and looks pretty
even. It doesn't (yet) link to the member directly though, which would
be really good for big structures or vfunc tables (where the
per-member kerneldoc tends to be long).

Also some minor drive-by polish where it makes sense, I read a lot
of docs ...

v2: Review from Gustavo.

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170125062657.19270-6-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_pci.c

@@ -223,7 +223,7 @@ void drm_pci_agp_destroy(struct drm_device *dev)
  * Try and register, if we fail to register, backout previous work.
  *
  * NOTE: This function is deprecated, please use drm_dev_alloc() and
- * drm_dev_register() instead and remove your ->load() callback.
+ * drm_dev_register() instead and remove your &drm_driver.load callback.
  *
  * Return: 0 on success or a negative error code on failure.
  */