ARM: plat-nomadik: move DMA40 header to <linux/platform_data>

This moves the DMA40 platform data header from <plat/ste_dma40.h>
to <linux/platform_data/dma-ste-dma40.h> where is belongs.

Cc: Dan Williams <djbw@fb.com>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Ola Lilja <ola.o.lilja@stericsson.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Andreas Westin <andreas.westin@stericsson.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>