You did not program your xipImage correctly into SPI flash.
Please verify that your image is correctly programmed into flash:
=> qspi dual
=> md 0x18200000
or
=> sf probe 0:1
=> sf read 0x08000000 100000 1000
=> md 0x08000000
then, compare to the binary contents of your xipImage file.
$ hexdump -C -n 100 output/linux-3.14/arch/arm/boot/xipImage
Chris