This should be used instead of hard coding the corresponding platforms.
The feature test macro is needed to support different SOCs in a single
kernel image.  While at it rename dma-mx1-mx2 to dma-v1 as mx25 doesn't
use it and so the mx2 part is wrong and move the header to
arch/arm/mach-imx.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>