ARM: ep93xx: vision_ep9307: enable DMA for SPI

Enable the 'use_dma' flag in the SPI platform data to improve the speed
of the mmc_spi driver.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>