I've used SPI flash with Xilinx boards, but I'm sure there are differences as 2.6.13 is pretty dusty.
You are correct to choose the M25P80 driver (probably, depending on your flash), but, you'll likely have to patch the driver so that the manufacturer/device ID of the particular flash you are using is included. in drivers/mtd/devices/m25p80.c edit the m25p_data array you include your particular flavor of SPI flash.
In a modern kernel, the device tree is used to specify what hardware is present. In these cases, you would need to manually edit the device tree to include the SPI flash (the XIlinx generator doesn't provide this mechanism). BlueCat, however, does not use a device tree. I cant guess how you indicate that a SPI flash is present (probably in the kernel source directly), or whether or not their BSP generator provides a mechanism to do so. So I'd recommend you to peek at the BlueCat documentation.