media: test-drivers: Rename second ioctl handlers argument to 'void *priv'

media: test-drivers: Rename second ioctl handlers argument to 'void *priv'

The second argument to the ioctl handlers is not a file handle any more.
Rename it from 'void *fh' to 'void *priv', to avoid misconceptions. This
is particularly important in test drivers as they are meant to be used
as reference implementations.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>