mtd: spi-nor: Skip erase logic when SPI_NOR_NO_ERASE is set

Even if SPI_NOR_NO_ERASE was set, one could still send erase opcodes
to the flash. It is not recommended to send unsupported opcodes to
flashes. Fix the logic and do not set mtd->_erase when SPI_NOR_NO_ERASE
is specified. With this users will not be able to issue erase opcodes to
flashes and instead they will recive an -ENOTSUPP error.

Fixes: b199489 ("mtd: spi-nor: add the framework for SPI NOR")
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Michael Walle <michael@walle.cc>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220228163334.277730-1-tudor.ambarus@microchip.com

Author: ambarus

drivers/mtd/spi-nor/core.c

@@ -2948,10 +2948,11 @@ static void spi_nor_set_mtd_info(struct spi_nor *nor)
 	mtd->flags = MTD_CAP_NORFLASH;
 	if (nor->info->flags & SPI_NOR_NO_ERASE)
 		mtd->flags |= MTD_NO_ERASE;
+	else
+		mtd->_erase = spi_nor_erase;
 	mtd->writesize = nor->params->writesize;
 	mtd->writebufsize = nor->params->page_size;
 	mtd->size = nor->params->size;
-	mtd->_erase = spi_nor_erase;
 	mtd->_read = spi_nor_read;
 	/* Might be already set by some SST flashes. */
 	if (!mtd->_write)