Add QSPI support (limited to read interface).
Implements the memory map and indirect modes.
Low level driver based on SPI-MEM operations.

Change-Id: Ied698e6de3c17d977f8b497c81f2e4a0a27c0961
Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Signed-off-by: Christophe Kerello <christophe.kerello@st.com>