mtd: autcpu12-nvram: drop frees of devm_ alloc'd data

devm free functions should not have to be explicitly used.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>