spi: move more spi_setup() functionality into core

Move some common spi_setup() error checks into the SPI framework from the
spi_master controller drivers:

 - Add a new "mode_bits" field to spi_master

 - Use that in spi_setup to validate the spi->mode value being
   requested.  Setting this new field is now mandatory for any
   controller supporting more than vanilla SPI_MODE_0.

 - Update all spi_master drivers to:

     * Initialize that field
     * Remove current spi_setup() checks using that value.

This is a net minor code shrink.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/spi/spi_bitbang.c b/drivers/spi/spi_bitbang.c
index 855b0b0..2a5abc0 100644
--- a/drivers/spi/spi_bitbang.c
+++ b/drivers/spi/spi_bitbang.c
@@ -188,12 +188,6 @@
 
 	bitbang = spi_master_get_devdata(spi->master);
 
-	/* Bitbangers can support SPI_CS_HIGH, SPI_3WIRE, and so on;
-	 * add those to master->flags, and provide the other support.
-	 */
-	if ((spi->mode & ~(SPI_CPOL|SPI_CPHA|bitbang->flags)) != 0)
-		return -EINVAL;
-
 	if (!cs) {
 		cs = kzalloc(sizeof *cs, GFP_KERNEL);
 		if (!cs)
@@ -452,6 +446,9 @@
 	spin_lock_init(&bitbang->lock);
 	INIT_LIST_HEAD(&bitbang->queue);
 
+	if (!bitbang->master->mode_bits)
+		bitbang->master->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;
+
 	if (!bitbang->master->transfer)
 		bitbang->master->transfer = spi_bitbang_transfer;
 	if (!bitbang->txrx_bufs) {