spi: spi-pxa2xx: remove legacy PXA DMA bits

Generic DMA support was already implemented by commit cd7bed00
("spi/pxa2xx: break out the private DMA API usage into a separate file")
which moved all the legacy PXA DMA implementation code into its own
file.

With generic DMA available for PXA, we can now just trash this file.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Acked-by: Mark Brown <broonie@linaro.org>
[respin after pxa dmaengine support upstream]
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>