media: staging: rkisp1: remove atomic operations for frame sequence

The isp.frame_sequence is now read only from the irq handlers
that are all fired from the same interrupt, so there is not need
for atomic operation.
In addition, the frame seq incrementation is moved from
rkisp1_isp_queue_event_sof to rkisp1_isp_isr to make the code
clearer and the incorrect inline comment is removed.

Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Acked-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>