sparc: Move of_set_property_mutex acquisition outside of devtree_lock grab.

Otherwise we try to sleep with preemption disabled, etc.

Noticed by Thomas Gleixner.
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/kernel/prom_common.c

@@ -79,6 +79,7 @@ int of_set_property(struct device_node *dp, const char *name, void *val, int len
 
 	err = -ENODEV;
 
+	mutex_lock(&of_set_property_mutex);
 	write_lock(&devtree_lock);
 	prevp = &dp->properties;
 	while (*prevp) {
@@ -88,9 +89,7 @@ int of_set_property(struct device_node *dp, const char *name, void *val, int len
 			void *old_val = prop->value;
 			int ret;
 
-			mutex_lock(&of_set_property_mutex);
 			ret = prom_setprop(dp->node, name, val, len);
-			mutex_unlock(&of_set_property_mutex);
 
 			err = -EINVAL;
 			if (ret >= 0) {
@@ -109,6 +108,7 @@ int of_set_property(struct device_node *dp, const char *name, void *val, int len
 		prevp = &(*prevp)->next;
 	}
 	write_unlock(&devtree_lock);
+	mutex_unlock(&of_set_property_mutex);
 
 	/* XXX Upate procfs if necessary... */