MIPS: IP27: Fix __node_distances undefined error

export the __node_distances symbol in the ip27 memory code to fix the
build error:

  Building modules, stage 2.
  MODPOST 311 modules
ERROR: "__node_distances" [drivers/block/nvme.ko] undefined!
scripts/Makefile.modpost:90: recipe for target '__modpost' failed

when building the kernel with:
 CONFIG_SGI_IP27=y
 CONFIG_BLK_DEV_NVME=m
Signed-off-by: NJames Cowgill <James.Cowgill@imgtec.com>
Cc: <stable@vger.kernel.org> # v3.15+
Reviewed-by: NJames Hogan <james.hogan@imgtec.com>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/sgi-ip27/ip27-memory.c

@@ -107,6 +107,7 @@ static void router_recurse(klrou_t *router_a, klrou_t *router_b, int depth)
 }
 
 unsigned char __node_distances[MAX_COMPACT_NODES][MAX_COMPACT_NODES];
+EXPORT_SYMBOL(__node_distances);
 
 static int __init compute_node_distance(nasid_t nasid_a, nasid_t nasid_b)
 {