[media] gsc-m2m: improve v4l2_capability driver and card fields

According to the V4L2 documentation the driver and card fields should be
used to identify the driver and the device but the gsc-m2m driver fills
those field using the platform device name, which in turn is the name of
the device DT node.

So not only the filled information isn't correct but also the same values
are used in the driver, card and bus_info fields.

Before this patch:

Driver Info (not using libv4l2):
        Driver name   : 13e00000.video-
        Card type     : 13e00000.video-scaler
        Bus info      : platform:13e00000.video-scaler
        Driver version: 4.7.0

After this patch:

Driver Info (not using libv4l2):
        Driver name   : exynos-gsc
        Card type     : exynos-gsc gscaler
        Bus info      : platform:13e00000.video-scaler
        Driver version: 4.7.0

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>