spi: Remove duplicate code to check chip_select

In spi_add_device(), we have the code to validate spi->chip_select.
So remove the duplicate code in various drivers.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@linaro.org>