mtd: spi-nor: allow registering multiple MTDs when DM is enabled

Currently when the SPI_FLASH_MTD config option is enabled, only one SPI
can be registered as MTD at any time - it is the last one probed (since
with old non-DM model only one SPI NOR could be probed at any time).

When DM is enabled, allow for registering multiple SPI NORs as MTDs by
utilizing the nor->mtd structure, which is filled in by spi_nor_scan
anyway, instead of filling a separate struct mtd_info.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Tested-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
Cc: Priyanka Jain <priyanka.jain@nxp.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Heiko Schocher <hs@denx.de>
Cc: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/drivers/mtd/spi/sf_mtd.c b/drivers/mtd/spi/sf_mtd.c
index 987fac2..94854fb 100644
--- a/drivers/mtd/spi/sf_mtd.c
+++ b/drivers/mtd/spi/sf_mtd.c
@@ -10,6 +10,20 @@
 #include <linux/mtd/mtd.h>
 #include <spi_flash.h>
 
+#if CONFIG_IS_ENABLED(DM_SPI_FLASH)
+
+int spi_flash_mtd_register(struct spi_flash *flash)
+{
+	return add_mtd_device(&flash->mtd);
+}
+
+void spi_flash_mtd_unregister(struct spi_flash *flash)
+{
+	del_mtd_device(&flash->mtd);
+}
+
+#else /* !CONFIG_IS_ENABLED(DM_SPI_FLASH) */
+
 static struct mtd_info sf_mtd_info;
 static bool sf_mtd_registered;
 static char sf_mtd_name[8];
@@ -123,7 +137,7 @@
 	return ret;
 }
 
-void spi_flash_mtd_unregister(void)
+void spi_flash_mtd_unregister(struct spi_flash *flash)
 {
 	int ret;
 
@@ -146,3 +160,5 @@
 	printf("Failed to unregister MTD %s and the spi_flash object is going away: you're in deep trouble!",
 	       sf_mtd_info.name);
 }
+
+#endif /* !CONFIG_IS_ENABLED(DM_SPI_FLASH) */