Add a SPI NAND framework based on the generic NAND framework and the
spi-mem infrastructure.

In its current state, this framework supports the following features:

- single/dual/quad IO modes
- on-die ECC

Signed-off-by: Peter Pan
Signed-off-by: Boris Brezillon
Signed-off-by: Miquel Raynal
Acked-by: Jagan Teki