media: vimc: fill in bus_info in media_device_info

It is good practice to fill in bus_info.

Also just use 'platform:vimc' when filling in the bus_info in querycap:
the bus_info has nothing to do with the video device name.

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