mtd: spi-nor: core: Remove reference to spi-nor.c

Remove the references to the old spi-nor.c file.
The old drivers/mtd/spi-nor/spi-nor.c file
is not more present and now some of its code is contained in:
drivers/mtd/spi-nor/core.c

Signed-off-by: Flavio Suligoi <f.suligoi@asem.it>
[tudor.ambarus@microchip.com:
- remove change in Documentation/driver-api/mtd/spi-nor.rst.
The documentation has to be rewritten entirely.
- update commit message]
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Link: https://lore.kernel.org/r/20210126092516.1431913-1-f.suligoi@asem.it

drivers/mtd/spi-nor/core.c

@@ -3453,8 +3453,8 @@ static void spi_nor_shutdown(struct spi_mem *spimem)
  * encourage new users to add support to the spi-nor library, and simply bind
  * against a generic string here (e.g., "jedec,spi-nor").
  *
- * Many flash names are kept here in this list (as well as in spi-nor.c) to
- * keep them available as module aliases for existing platforms.
+ * Many flash names are kept here in this list to keep them available
+ * as module aliases for existing platforms.
  */
 static const struct spi_device_id spi_nor_dev_ids[] = {
 	/*