spi: spi-davinci: Don't error when SPI_CS_WORD and cs_gpio

This remove the check and subsequent return of error for the case when
a SPI device requires SPI_CS_WORD and is also configured to use a GPIO
for the CS line.

Commit a134cc414e86 ("spi: always use software fallback for SPI_CS_WORD
when using cs_gio") handles this case now, so this check is no longer
necessary.

Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Mark Brown <broonie@kernel.org>