accel/ivpu: Disallow re-exporting imported GEM objects

accel/ivpu: Disallow re-exporting imported GEM objects

Prevent re-exporting of imported GEM buffers by adding a custom
prime_handle_to_fd callback that checks if the object is imported
and returns -EOPNOTSUPP if so.

Re-exporting imported GEM buffers causes loss of buffer flags settings,
leading to incorrect device access and data corruption.

Reported-by: Yametsu <yam3tsu@gmail.com>
Fixes: 57557964b582 ("accel/ivpu: Add support for userptr buffer objects")
Reviewed-by: Andrzej Kacprowski <andrzej.kacprowski@linux.intel.com>
Signed-off-by: Karol Wachowski <karol.wachowski@linux.intel.com>
Cc: <stable@vger.kernel.org> # v6.19+