ARM: mxs-dma: include <linux/dmaengine.h>

ARM: mxs-dma: include <linux/dmaengine.h>

Other files using dma.h may fail to compile as follows:
In file included from sound/soc/mxs/mxs-pcm.h:22,
                 from sound/soc/mxs/mxs-saif.h:112,
                 from sound/soc/mxs/mxs-sgtl5000.c:34:
arch/arm/mach-mxs/include/mach/dma.h:16: warning: 'struct dma_chan' declared inside parameter list
arch/arm/mach-mxs/include/mach/dma.h:16: warning: its scope is only this definition or declaration, which is probably not what you want
arch/arm/mach-mxs/include/mach/dma.h: In function 'mxs_dma_is_apbh':
arch/arm/mach-mxs/include/mach/dma.h:18: error: dereferencing pointer to incomplete type
arch/arm/mach-mxs/include/mach/dma.h: At top level:
arch/arm/mach-mxs/include/mach/dma.h:21: warning: 'struct dma_chan' declared inside parameter list
arch/arm/mach-mxs/include/mach/dma.h: In function 'mxs_dma_is_apbx':
arch/arm/mach-mxs/include/mach/dma.h:23: error: dereferencing pointer to incomplete type
make[3]: *** [sound/soc/mxs/mxs-sgtl5000.o] Error 1
make[2]: *** [sound/soc/mxs] Error 2
make[1]: *** [sound/soc] Error 2
make: *** [sound] Error 2

It seems it's better for dma.h to include dmaengine.h himself.

Signed-off-by: Dong Aisheng <b29396@freescale.com>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>