mtd: atmel_nand: use devm_xxx gpio kzalloc, gpio and ioremap

this will allow to simply the error and remove path

Cc: linux-mtd@lists.infradead.org
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
[josh.wu@atmel.com: fix checkpatch warnings and rebase to latest mtd git tree]
[josh.wu@atmel.com: replace devm_request_and_ioremap with devm_ioremap_resource]
Signed-off-by: Josh Wu <josh.wu@atmel.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>