MIPS: Netlogic: Add macro for node present

Add macro nlm_node_present() that can be used to check if a node is present
in a multi-chip configuration. This can be used even when NUMA is not enabled.

Signed-off-by: Jayachandran C <jchandra@broadcom.com>
Signed-off-by: John Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/6272/