ARC: [plat-eznps] Fix build error

commit 6492f09e864417d382e22b922ae30693a7ce2982 upstream.

Make ATOMIC_INIT available for all ARC platforms (including plat-eznps)

Signed-off-by: Noam Camus <noamca@mellanox.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>