etnaviv: initialize vertex attributes on context reset

etnaviv: initialize vertex attributes on context reset

It seems that at least some GC400 come out of reset with random vertex
attributes enabled and also don't disable them on the write to the first
config register as normal. Enabling all attributes seems to provide the
GPU with the required edge to actually disable the unused attributes on
the next draw.

Cc: mesa-stable
Reported-by: Steven Walter
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14285>