spi: spi-bfin5xx: Initialize cr_width in bfin_spi_pump_transfers()

spi: spi-bfin5xx: Initialize cr_width in bfin_spi_pump_transfers()

cr_width may be not initialized before using by cr, the related warning
(with defconfig under blackfin by gcc5):

    CC      drivers/spi/spi-bfin5xx.o
  drivers/spi/spi-bfin5xx.c: In function 'bfin_spi_pump_transfers':
  drivers/spi/spi-bfin5xx.c:655:5: warning: 'cr_width' may be used uninitialized in this function [-Wmaybe-uninitialized]
    cr |= cr_width;
       ^

Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>