The Micron N25Q512 flash devices are not supported. This flash is a multi-die device.
The Micron multi-die SPI Flash parts (N25Q512A and N25Q00AA) have a read limitation which keeps any usable bitstream stored on the flash to 256 Mb or less.
When a read reaches the end of one of the dies, that read does not cross the die boundary but wraps back around to the start of the same die from which the read began.
From the 512 Mb data sheet:
"After any READ command is executed, the device will output data from the selected address in the die.
After a die boundary is reached, the device will start reading again from the beginning of the same 256Mb die."
Refer to the data sheet for read operation details for the Micron N25Q512 flash:
This read limitation of the multi-die SPI Flash device makes it incompatible with Xilinx FPGAs.
Beginning in Vivado 2014.2, Xilinx supports the N25Q replacement, the MT25Q.
The MT25Q devices are supported for FPGA configuration.
This also includes the multi-die parts in the family.