mtd: spi-nor: change "error reading JEDEC id" from dbg to err

In case of SPI error during the reading of the nor Id,
the probe fails without any error message related to
the JEDEC Id reading procedure.

Signed-off-by: Flavio Suligoi <f.suligoi@asem.it>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>