gpu: ipu-v3: image-convert: Remove need_abort flag

The need_abort flag is not really needed anymore in
__ipu_image_convert_abort(), remove it.
No functional changes.

Signed-off-by: Steve Longerbeam <slongerbeam@gmail.com>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>