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/orion_spi.c b/drivers/spi/orion_spi.c
index 6d5e33b..3aea50d 100644
--- a/drivers/spi/orion_spi.c
+++ b/drivers/spi/orion_spi.c
@@ -358,12 +358,6 @@
 
 	orion_spi = spi_master_get_devdata(spi->master);
 
-	if (spi->mode) {
-		dev_err(&spi->dev, "setup: unsupported mode bits %x\n",
-			spi->mode);
-		return -EINVAL;
-	}
-
 	/* Fix ac timing if required.   */
 	if (orion_spi->spi_info->enable_clock_fix)
 		orion_spi_setbits(orion_spi, ORION_SPI_IF_CONFIG_REG,
@@ -473,6 +467,9 @@
 	if (pdev->id != -1)
 		master->bus_num = pdev->id;
 
+	/* we support only mode 0, and no options */
+	master->mode_bits = 0;
+
 	master->setup = orion_spi_setup;
 	master->transfer = orion_spi_transfer;
 	master->num_chipselect = ORION_NUM_CHIPSELECTS;