mtd: rawnand: Fix probe failure due to of_get_nand_secure_regions()

Due to 14f97f0b, the rawnand platforms without "secure-regions"
property defined in DT fails to probe. The issue is,
of_get_nand_secure_regions() errors out if
of_property_count_elems_of_size() returns a negative error code.

If the "secure-regions" property is not present in DT, then also we'll
get -EINVAL from of_property_count_elems_of_size() but it should not
be treated as an error for platforms not declaring "secure-regions"
in DT.

So fix this behaviour by checking for the existence of that property in
DT and return 0 if it is not present.

Fixes: 14f97f0b ("mtd: rawnand: Add a check in of_get_nand_secure_regions()")
Reported-by: Martin Kaiser <martin@kaiser.cx>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Martin Kaiser <martin@kaiser.cx>
Tested-by: Martin Kaiser <martin@kaiser.cx>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210727062813.32619-1-manivannan.sadhasivam@linaro.org

drivers/mtd/nand/raw/nand_base.c

@@ -5228,8 +5228,14 @@ static bool of_get_nand_on_flash_bbt(struct device_node *np)
 static int of_get_nand_secure_regions(struct nand_chip *chip)
 {
 	struct device_node *dn = nand_get_flash_node(chip);
+	struct property *prop;
 	int nr_elem, i, j;
 
+	/* Only proceed if the "secure-regions" property is present in DT */
+	prop = of_find_property(dn, "secure-regions", NULL);
+	if (!prop)
+		return 0;
+
 	nr_elem = of_property_count_elems_of_size(dn, "secure-regions", sizeof(u64));
 	if (nr_elem <= 0)
 		return nr_elem;