linux-phytec-fsl

mtd: kill dev_to_mtd helper

... since it is not needed because the generic 'dev_get_drvdata()' can be
used instead.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>