media: atomisp: make atomisp_css_stop() void

The return value of atomisp_css_stop() function is always 0 and there
are no callers check the return value, so there's no reason for a return
value. Convert atomisp_css_stop() to a void function.

Link: https://lore.kernel.org/linux-media/1605359976-11254-1-git-send-email-kaixuxia@tencent.com


Reported-by: Tosk Robot <tencent_os_robot@tencent.com>
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>