mtd: rawnand: Deprecate ->chip_delay

The wait timeouts and delays are directly extracted from the NAND
timings and ->chip_delay is only used in legacy path, so let's move it
to the nand_legacy struct to make it clear.

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>