media: rkisp1: rksip1-capture.c: Improve comments and fix typos

Improve the wording of the function description to increase readability.

Fix three typos:
s/during processing a frame/while processing a frame/
s/it also update/it also updates/
s/there's not buf in shadow/there's no buffer in a shadow register/

Replace the abbreviation 'buf' with the full word buffer, the
abbreviation 'config' with the verb configure, and 'regs' with registers.
The goal of this change is to ease the reading flow of the comment.

Signed-off-by: Sebastian Fricke <sebastian.fricke@posteo.net>
Reviewed-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>