media: hantro: Rename {prepare,finish}_run to {start,end}_prepare_run

hantro_prepare_run() and hantro_finish_run() are
slightly misleading, so let's rename it to something
a bit more clear.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>