panfrost: Remove sync arguments from panfrost_batch_submit

Whether a sync object is used cannot depend on where the batch is
submitted from, remove the in_sync and out_sync fields from
panfrost_batch_submit.

Always use an output syncobj, this is required for glFinish to work
correctly. This could be skipped for batches which another batch
depends on, but because of the existence of empty batches which emit
no job, doing so is not trivial.

Never use an input syncobj. There appears to be no point to this, the
kernel driver does implicit sync anyway.

Fixes "seconds per frame" rendering with Neverball; previously, every
batch was submitted with out_sync=0, so DRI's frame throttling could
do nothing. New jobs would keep getting submitted until more than a
thousand were queued in the kernel, which increased rendering latency
for the compositor far beyond acceptable levels.

Cc: mesa-stable
Part-of: <!16966>
49 jobs for !16966 with neverfps in 24 minutes and 25 seconds (queued for 6 seconds)
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