spi: pxa2xx: Print actual DMA/PIO transfer mode in debug messages

Transfer debug messages don't actually show is the transfer really using
DMA. Driver may fall back to PIO in case transfer size is not within the
certain limits or fails to map DMA buffers but debug messages don't reveal
that.

Move these debug messages further in pump_transfers() where the actual
transfer mode is known and use drv_data->dma_mapped flag instead of
chip->enable_dma for printing the mode.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>