media: v4l2-event: Modified variable type 'unsigned' to 'unsigned int'

Prefer 'unsigned int' to bare use of 'unsigned'.
So modified variable type 'unsigned' to 'unsigned int' in v4l2-event.c.

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