mtd: atmel_nand: replace cpu_is_at32ap7000() with a nand platform data

The nand driver use cpu_is_at32ap7000() macro for a workaround. For the
multi-platform support, we will remove this cpu_is_xxx() macro.

This patch adds a boolean variable need_reset_workaround in structure
atmel_nand_data. Using this variable we can remove cpu_is_at32ap7000() macro.

Hans-Christian: Feel free to push this through the mtd tree, if they won't
accept it I'm working on getting my workflow up on the linux-avr32.git tree.

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Acked-by: Hans-Christian Egtvedt <egtvedt@samfundet.no>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>