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 <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 0db5d64..9c4cd27 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -245,6 +245,9 @@
 	 */
 	u16			dma_alignment;
 
+	/* spi_device.mode flags understood by this controller driver */
+	u16			mode_bits;
+
 	/* Setup mode and clock, etc (spi driver may call many times).
 	 *
 	 * IMPORTANT:  this may be called when transfers to another