nand: lpc32xx: add SLC NAND controller support

The change adds support of LPC32xx SLC NAND controller.

LPC32xx SoC has two different mutually exclusive NAND controllers to
communicate with single and multiple layer chips.

This simple driver allows to specify NAND chip timings and defines
custom read_buf()/write_buf() operations, because access to 8-bit data
register must be 32-bit aligned.

Support of hardware ECC calculation is not implemented (data
correction is always done by software), since it requires a working
DMA engine.

The driver can be included to an SPL image.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Acked-by: Scott Wood <scottwood@freescale.com>
Tested-by: Sylvain Lemieux <slemieux@tycoint.com>