spi: dw: remove bits_per_word member of struct chip_data

There is no need to carry over spi->bits_per_word and Co from ->setup() in
struct chip_data since ->transfer_one() will anyway take the transfer
parameters from struct spi_transfer. This is since SPI core validates both
bits_per_word transfer parameter and defaults to spi->bits_per_word in case
that per transfer parameter is not set.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>