mtd: dataflash: Add device-tree SPI IDs

Commit 5fa6863b ("spi: Check we have a spi_device_id for each DT
compatible") added a test to check that every SPI driver has a
spi_device_id for each DT compatiable string defined by the driver
and warns if the spi_device_id is missing. The spi_device_ids are
missing for the dataflash driver and the following warnings are now
seen.

 WARNING KERN SPI driver mtd_dataflash has no spi_device_id for atmel,at45
 WARNING KERN SPI driver mtd_dataflash has no spi_device_id for atmel,dataflash

Fix this by adding the necessary spi_device_ids.

Fixes: 96c8395e ("spi: Revert modalias changes")
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20211130112443.107730-1-jonathanh@nvidia.com