media: atomisp: Fix support for time 64 API

The time 64 API patchset changed the ts stamp to u64.

Update this driver accordingly.

Fixes: 15a40b27

 ("media: videobuf: use u64 for the timestamp internally")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>