spi/pl022: Devicetree support w/o platform data

Even with devicetree support, we needed platform data to provide some data,
leading to mixed device tree and platform data. This patch makes it possible to
provide all that information via device tree. Now, the data must be provided
via platform data _or_ device tree completely.

Only in case of DMA where a callback specification is necessary (dma_filter()),
platform data is the only option.

Signed-off-by: Roland Stigge <stigge@antcom.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>