Commit 24778be2 "spi: convert drivers to use bits_per_word_mask" removed
what appeared to be redundant code from many drivers. However, it
appears that in the spi-bitbang case, these functions are required by
the spi-bitbang core, even if they don't do anything. Restore them.

For 3.12, the spi-bitbang core should be adjusted not to require these
callbacks to exist if they don't need to do anything.

This is the equivalent of Michal Simek's patch "spi/xilinx: Revert
master->setup function removal", applied to other affected drivers.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@linaro.org>