[media] v4l: ti-vpe: Use correct bus_info name for the device in querycap

The bus_info parameter in v4l2_capabilities expects a 'platform_' prefix. This
wasn't done in the driver and hence was breaking compliance. Update the bus_info
parameter accordingly.

Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Archit Taneja <archit@ti.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>