mmc: spi: 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_id is
missing for the MMC SPI driver and the following warning is now seen.

 WARNING KERN SPI driver mmc_spi has no spi_device_id for mmc-spi-slot

Fix this by adding the necessary spi_device_id.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Link: https://lore.kernel.org/r/20211115113813.238044-1-jonathanh@nvidia.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>