ARC: CONFIG_NODES_SHIFT fix default values

Seem like values assigned as absolute number and not and
shift value, i.e. should be 0 for one node (2^0) and 1 for
couple of nodes (2^1)

Signed-off-by: Noam Camus <noamca@mellanox.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>