erlang: use erlang's native atomic ops

erlang: use erlang's native atomic ops

Now that we're using Erlang 18, the preferred atomic ops implementation
for Erlang is its own built-in implementation, so use it instead of
libatomic_ops. BR2_PACKAGE_ERLANG_ARCH_SUPPORTS is added now that
BR2_PACKAGE_LIBATOMIC_OPS_ARCH_SUPPORTS can no longer be used for
checking whether the package can be built.

This fixes autobuilder failures on aarch64 and sparc_v8:

http://autobuild.buildroot.net/results/0cd/0cd22eb74fa29e5a85bf897762e16ab3daf33962/
http://autobuild.buildroot.net/results/688278236e6d5bcd63b7d4413303eb115a38f3a7/
http://autobuild.buildroot.net/results/7875a7425bfe1f43d46c9a1db9f96b54f7a99b19/

Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>