powerpc: Drop GPL from of_node_to_nid() export to match other arches

The generic implementation of of_node_to_nid() is EXPORT_SYMBOL, added
in commit 298535c00a2c ("of, numa: Add NUMA of binding
implementation.").

The powerpc implementation added in commit 953039c8df7b ("[PATCH]
powerpc: Allow devices to register with numa topology") is
EXPORT_SYMBOL_GPL.

This creates an inconsistency for of_node_to_nid() callers across
architectures.

Update the powerpc implementation to be exported consistently with the
generic implementation.

Signed-off-by: Shailendra Singh <shailendras@nvidia.com>
Reviewed-by: Andy Ritger <aritger@nvidia.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/numa.c

@@ -290,7 +290,7 @@ int of_node_to_nid(struct device_node *device)
 
 	return nid;
 }
-EXPORT_SYMBOL_GPL(of_node_to_nid);
+EXPORT_SYMBOL(of_node_to_nid);
 
 static int __init find_min_common_depth(void)
 {