spi: pxa2xx: Remove cr0 variable from struct chip_data

There hasn't been need to carry chip->cr0 after SPI core started to
validate speed_hz and bits_per_word transfer parameters. That effectively
caused that pump_transfers() always recalculated it and practically
chip->cr0 is used locally in setup() for debug prints only.

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