Up to now the SPI alias was used as an index into an array defined in
the SPI driver to determine the SPI FIFO depth. Drop the dependency on
the SPI alias and specify the SPI FIFO depth directly into the SPI node.

There are no SPI aliases defined, thus the FIFO depth was determined by
matching the FIFO depth of the I2C node of the same USI parent.
No functional change expected.
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Link: https://lore.kernel.org/r/20240216140449.2564625-7-tudor.ambarus@linaro.orgSigned-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>