mtd: rawnand: macronix: Add support for deep power down mode

Macronix AD series support deep power down mode for a minimum
power consumption state.

Overload nand_suspend() & nand_resume() in Macronix specific code to
support deep power down mode.

Signed-off-by: Mason Yang <masonccyang@mxic.com.tw>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>