etnaviv: Rework locking

Replace the per-screen locking of flushing with per-context one and
add per-context lock around command stream buffer accesses, to prevent
cross-context flushing from corrupting these command stream buffers.

Signed-off-by: Marek Vasut <marex@denx.de>
49 jobs for !2001 with resource_sharing-v7 in 19 seconds (queued for 6 seconds)
latest merge request