ARC: [plat-eznps] disabled stall counter due to a HW bug

This counter represents threshold for consecutive stall which
would trigger HW threads scheduling. However when enabled, low
threshhold values cause performance degradation and in the
worst case even livelock.

So disable it by resorting to HW reset value

Signed-off-by: Noam Camus <noamca@mellanox.com>
Reviewed-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
[vgupta: fixed changelog]