[POWERPC] spi: mode should be "cpu-qe" instead of "qe"

Mode should be "cpu-qe" for QE in CPU mode. "qe" should be reserved
for native QE mode.
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

Documentation/powerpc/booting-without-of.txt

@@ -1551,7 +1551,7 @@ platforms are moved over to use the flattened-device-tree model.
    Required properties:
    - device_type : should be "spi".
    - compatible : should be "fsl_spi".
-   - mode : the SPI operation mode, it can be "cpu" or "qe".
+   - mode : the SPI operation mode, it can be "cpu" or "cpu-qe".
    - reg : Offset and length of the register set for the device
    - interrupts : <a b> where a is the interrupt number and b is a
      field that represents an encoding of the sense and level