of_mtd: Add no-op stubs to support CONFIG_OF=n

Just like the rest of the subsystems, let's add the required no-op
functions to implement stubs when CONFIG_OF=n.

This prevents MTD drivers from having ugly ifdefs in their code,
and instead hide the ifdef monster in the header closet (far away
from people's sight).
Signed-off-by: NEzequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: NBrian Norris <computersforpeace@gmail.com>

include/linux/of_mtd.h

@@ -10,10 +10,29 @@
 #define __LINUX_OF_NET_H
 
 #ifdef CONFIG_OF_MTD
+
 #include <linux/of.h>
 int of_get_nand_ecc_mode(struct device_node *np);
 int of_get_nand_bus_width(struct device_node *np);
 bool of_get_nand_on_flash_bbt(struct device_node *np);
-#endif
+
+#else /* CONFIG_OF_MTD */
+
+static inline int of_get_nand_ecc_mode(struct device_node *np)
+{
+	return -ENOSYS;
+}
+
+static inline int of_get_nand_bus_width(struct device_node *np)
+{
+	return -ENOSYS;
+}
+
+static inline bool of_get_nand_on_flash_bbt(struct device_node *np)
+{
+	return false;
+}
+
+#endif /* CONFIG_OF_MTD */
 
 #endif /* __LINUX_OF_MTD_H */