mtd: nand: Remove jz4740 driver

This driver is not used by anyone, remove it.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Scott Wood <oss@buserror.net>
Acked-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Signed-off-by: Scott Wood <oss@buserror.net>