spi: Add Cadence QSPI DM driver used by SoCFPGA

This driver is cloned from the Altera Rockerboard.org U-Boot
repository. I used this git tag: ACDS14.0.1_REL_GSRD_RC2. With Some
modification to support the U-Boot driver model (DM).

As mentioned above, in this new version I ported this driver to the
new driver model (DM). One big advantage of this move is that now
multiple SPI drivers can be enabled on one platform. And since the
SoCFPGA also has the Designware SPI master controller integrated,
this feature is really needed to support both controllers.

Because of this, this series needs the DT support for SoCFPGA
to be applied. For DT based probing in the SPI DM.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Chin Liang See <clsee@altera.com>
Cc: Dinh Nguyen <dinguyen@altera.com>
Cc: Vince Bridgers <vbridger@altera.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Pavel Machek <pavel@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>