gpu: ipu-v3: image-convert: Allow reentrancy into abort

Allow reentrancy into ipu_image_convert_abort(), by moving re-init
of ctx->aborted completion under the spin lock, and only if there is
an active run, and complete all waiters do_bh(). Note:
ipu_image_convert_unprepare() is still _not_ reentrant, and can't
be made reentrant.

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>