mtd: physmap-core: Restore map_rom fallback

When the exact mapping type driver was not available, the old
physmap_of_core driver fell back to mapping the region as ROM.
Unfortunately this feature was lost when the DT and pdata cases were
merged.  Revive this useful feature.

Fixes: 642b1e8d ("mtd: maps: Merge physmap_of.c into physmap-core.c")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/550e8c8c1da4c4baeb3d71ff79b14a18d4194f9e.1693407371.git.geert+renesas@glider.be

drivers/mtd/maps/physmap-core.c

@@ -551,6 +551,17 @@ static int physmap_flash_probe(struct platform_device *dev)
 		if (info->probe_type) {
 			info->mtds[i] = do_map_probe(info->probe_type,
 						     &info->maps[i]);
+
+			/* Fall back to mapping region as ROM */
+			if (!info->mtds[i] && IS_ENABLED(CONFIG_MTD_ROM) &&
+			    strcmp(info->probe_type, "map_rom")) {
+				dev_warn(&dev->dev,
+					 "map_probe() failed for type %s\n",
+					 info->probe_type);
+
+				info->mtds[i] = do_map_probe("map_rom",
+							     &info->maps[i]);
+			}
 		} else {
 			int j;