SPI controller drivers: check for unsupported modes

Minor SPI controller driver updates: make the setup() methods reject
spi->mode bits they don't support, by masking aginst the inverse of bits
they *do* support.  This insures against misbehavior later when new mode
bits get added.

Most controllers can't support SPI_LSB_FIRST; more handle SPI_CS_HIGH.
Support for all four SPI clock/transfer modes is routine.

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/atmel_spi.c b/drivers/spi/atmel_spi.c
index 8b2601d..7524a84 100644
--- a/drivers/spi/atmel_spi.c
+++ b/drivers/spi/atmel_spi.c
@@ -350,6 +350,7 @@
 	return ret;
 }
 
+/* the spi->mode bits understood by this driver: */
 #define MODEBITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH)
 
 static int atmel_spi_setup(struct spi_device *spi)