spi: spi-mem: add stm32 qspi controller

The qspi controller is a specialized communication interface
targeting single, dual or quad SPI Flash memories (NOR/NAND).

It can operate in any of the following modes:
-indirect mode: all the operations are performed using the quadspi
 registers
-read memory-mapped mode: the external Flash memory is mapped to the
 microcontroller address space and is seen by the system as if it was
 an internal memory

tested on:
-NOR: mx66l51235l
-NAND: MT29F2G01ABAGD

Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
Signed-off-by: Mark Brown <broonie@kernel.org>