drm/panthor: Fix some kerneldoc warnings

When compiling with W=1 the build process will flag empty comments,
misnamed documented variables and incorrect tagging of functions.
Fix them in one go.

Fixes: de854881 ("drm/panthor: Add the scheduler logical block")
Cc: Boris Brezillon <boris.brezillon@collabora.com>
Cc: Steven Price <steven.price@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240402215423.360341-2-liviu.dudau@arm.com