media: sh: migor: Include missing dma-mapping header

Since the removal of the stale soc_camera headers, Migo-R board fails to
build due to missing dma-mapping include directive.

Include missing dma-mapping.h header in Migo-R board file to fix the build
error.

Fixes: a50c7738 ("media: sh: migor: Remove stale soc_camera include")

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>