[POWERPC] Don't complain if size-cells == 0 in prom_parse()

An mdio bus scan was added with ucc_geth phylib
migration patches, now machines complain on boot, saying:

prom_parse: Bad cell count for /qe@e0100000/mdio@2120/ethernet-phy@00
prom_parse: Bad cell count for /qe@e0100000/mdio@2120/ethernet-phy@01

since size-cells can indeed be 0, this patch fixes the check.
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/prom_parse.c

@@ -24,7 +24,7 @@
 /* Max address size we deal with */
 #define OF_MAX_ADDR_CELLS	4
 #define OF_CHECK_COUNTS(na, ns)	((na) > 0 && (na) <= OF_MAX_ADDR_CELLS && \
-			(ns) > 0)
+			(ns) >= 0)
 
 static struct of_bus *of_match_bus(struct device_node *np);
 static int __of_address_to_resource(struct device_node *dev,