media: atomisp: Remove custom sysfs attributes from atomisp_drvfs.c

Continue the cleanup of the AtomISP driver, as discussed with Hans and Andy
in [1].

Tackle TODO item: "Remove custom sysfs files created by atomisp_drvfs.c":
- Remove the sysfs attributes `dbglvl`, `dbgfun`, and `dbgopt`.
- Delete their associated show/store handler functions.
- Remove the corresponding attribute group definitions.

Link: https://lore.kernel.org/all/836dc6b6-2821-47fc-8f24-0838f979af76@kernel.org/

 [1]
Suggested-by: Hans de Goede <hansg@kernel.org>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Abdelrahman Fekry <abdelrahmanfekry375@gmail.com>
Link: https://lore.kernel.org/r/20250704161051.16733-1-abdelrahmanfekry375@gmail.com


[hansg@kernel.org: Completely remove the now empty atomisp_drvfs files]
Reviewed-by: Hans de Goede <hansg@kernel.org>
Signed-off-by: Hans de Goede <hansg@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>