Add SPI-NAND framework ...

This framework supports SPI-NAND and is based on the
SPI-MEM framework for SPI operations. It uses a common high
level access using the io_mtd.

It is limited to the read functionalities.

Default behavior is the basic one data line operation
but it could be overridden by platform.

Change-Id: Icb4e0887c4003a826f47c876479dd004a323a32b
Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Signed-off-by: Christophe Kerello <christophe.kerello@st.com>