stm32mp1: Add support for SPI-NAND boot device

STM32MP1 platform is able to boot from SPI-NAND devices.
These modifications add this support using the new
SPI-NAND framework.

Change-Id: I0d5448bdc4bde153c1209e8043846c0f935ae5ba
Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
6 files changed