mtd: spi-nor: intel-spi: Add support for Intel Elkhart Lake SPI serial flash

Intel Elkhart Lake has the same SPI serial flash controller as Ice Lake.
Add Elkhart Lake PCI ID to the driver list of supported devices.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>