spi: xilinx: Add support for xlnx,axi-quad-spi-1.00.a

spi: xilinx: Add support for xlnx,axi-quad-spi-1.00.a

The driver has been successfully tested with Xilinx's core
axi-quad-spi-1.0.0a. Documented on DS843:

https://www.xilinx.com/support/documentation/ip_documentation/axi_quad_spi/v1_00_a/ds843_axi_quad_spi.pdf

Cc: Mark Brown <broonie@kernel.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: devicetree@vger.kernel.org
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>