Blackfin: boards: clean up redundant/dead spi resources

The default for the Blackfin SPI driver is 8 bits and dma disabled,
so many of the bfin5xx_spi_chip resources are redundant.  So punt
those parts.

Further, drivers should themselves be declaring 16 bit transfers,
so for those that do, and for the ones which no longer do 16 bit
transfers, drop the bfin5xx_spi_chip resources.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>