spi: Fix WARN when removing spi-fsl-spi module

If CPM mode is not used, the fsl_dummy_rx variable is never allocated.  When
the cleanup attempts to free it, the reference count is zero and a WARN is
generated.  The same CPM mode check used in the initialize is applied to the
free as well.

Tested on 2.6.33 with the previous spi_mpc8xxx driver.  The renamed
spi-fsl-spi driver looks to have the same problem.
Signed-off-by: NJeff Harris <jeff_harris@kentrox.com>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

drivers/spi/spi-fsl-spi.c

@@ -825,6 +825,9 @@ static void fsl_spi_cpm_free(struct mpc8xxx_spi *mspi)
 {
 	struct device *dev = mspi->dev;
 
+	if (!(mspi->flags & SPI_CPM_MODE))
+		return;
+
 	dma_unmap_single(dev, mspi->dma_dummy_rx, SPI_MRBLR, DMA_FROM_DEVICE);
 	dma_unmap_single(dev, mspi->dma_dummy_tx, PAGE_SIZE, DMA_TO_DEVICE);
 	cpm_muram_free(cpm_muram_offset(mspi->tx_bd));