of: Fix iteration bug over CPU reg properties

The size of each hwid in a cpu nodes 'reg' property is defined by the
parents #address-cells property in the normal way. The cpu parsing code
has a bug where it will overrun the end of the property if
address-cells is greater than one. This commit fixes the problem by
adjusting the array size by the number of address cells. It also makes
sure address-cells isn't zero for that would cause an infinite loop.

v2: bail if #address-cells is zero instead of forcing to
    OF_ROOT_NODE_ADDR_CELLS_DEFAULT. Forcing it will cause the reg
    property to be parsed incorrectly.

Signed-off-by: Grant Likely <grant.likely@linaro.org>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>

drivers/of/base.c

@@ -265,9 +265,9 @@ static bool __of_find_n_match_cpu_property(struct device_node *cpun,
 
 	ac = of_n_addr_cells(cpun);
 	cell = of_get_property(cpun, prop_name, &prop_len);
-	if (!cell)
+	if (!cell || !ac)
 		return false;
-	prop_len /= sizeof(*cell);
+	prop_len /= sizeof(*cell) * ac;
 	for (tid = 0; tid < prop_len; tid++) {
 		hwid = of_read_number(cell, ac);
 		if (arch_match_cpu_phys_id(cpu, hwid)) {