mtd: nand: mxc_nand: Remove unneeded check for platform_get_resource()

devm_ioremap_resource() checks its arguments, so there is no need for
explicitly checking the return value from platform_get_resource().

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>