media: exynos4-is: don't rely on the v4l2_async_subdev internals

Commit 1f391df4 ("media: v4l2-async: Use endpoints in
__v4l2_async_nf_add_fwnode_remote()") changed the data that is stored in
the v4l2_async_subdev internals from the fwnode pointer to the parent
device to the fwnode pointer to the matched endpoint. This broke the
sensor matching code, which relied on the particular fwnode data in the
v4l2_async_subdev internals. Fix this by simply matching the
v4l2_async_subdev pointer, which is already available there.

Reported-by: Daniel Scally <djrscally@gmail.com>
Fixes: fa91f105 ("[media] exynos4-is: Add support for asynchronous subdevices registration")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Daniel Scally <djrscally@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>