boards: arm: arty: designstart_m1: enable Xilinx AXI Quad SPI instances

Add the Xilinx AXI Quad SPI IP instances present in the ARM Cortex-M1
DesignStart FPGA reference design and enable the instance connected to
the onboard SPI NOR flash containing the FPGA configuration bitstream.

Signed-off-by: Henrik Brix Andersen <henrik@brixandersen.dk>