User arguments passed to .get/set_fmt() pad operation callbacks may
contain unsupported values.  The driver takes control over frame size
and pixel code as well as colorspace and field attributes but has never
cared for remainig format attributes, i.e., ycbcr_enc, quantization
and xfer_func, introduced by commit 11ff030c ("[media]
v4l2-mediabus: improve colorspace support").  Fix it.

Set up a static v4l2_mbus_framefmt structure with attributes
initialized to reasonable defaults and use it for updating content of
user provided arguments.  In case of V4L2_SUBDEV_FORMAT_ACTIVE,
postpone frame size update, now performed from inside ov6650_s_fmt()
helper, util the user argument is first updated in ov6650_set_fmt() with
default frame format content.  For V4L2_SUBDEV_FORMAT_TRY, don't copy
all attributes to pad config, only those handled by the driver, then
fill the response with the default frame format updated with resulting
pad config format code and frame size.

Fixes: 11ff030c ("[media] v4l2-mediabus: improve colorspace support")
Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>