spi: pxa2xx: Remove rx_/tx_map_len members from struct driver_data

spi: pxa2xx: Remove rx_/tx_map_len members from struct driver_data

spi-pxa2xx-dma.c DMA engine implementation stopped using PIO for
unaligned trailing bytes in the commit 111e0a9dc71e ("spi/pxa2xx: Prevent
DMA from transferring too many bytes"). This means there is no need to
update tx/rx transfer buffer pointers after DMA completion. These buffer
pointers will be set to new buffers when handling the next transfer.

Because this buffer pointer update was only remaining use for rx_map_len
and tx_map_len members in struct driver_data after removing the legacy PXA
DMA implementation they can be removed now.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Mark Brown <broonie@kernel.org>