Renamed bitbang_transfer_setup to follow convention of other exported symbols
from spi-bitbang.  Exported spi_bitbang_setup_transfer to allow users of
spi-bitbang to use the function in their own setup_transfer.
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>