media: staging: rkisp1: stats: read the stats in the isr

Currently the stats are read in a work queue. Defering the
reading of the stats is not needed and it is fine to read them
inside the irq handler.
This patch fixes and remove the TODO item:
'Use threaded interrupt for rkisp1_stats_isr(), remove work queue.'

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>