[PATCH] spi: fix error setting the spi mode in pxa2xx_spi.c

Currently the spi mode can be set to the wrong mode if you are switching
from any mode other than mode 0.  This is because the mode is set using a
bitwise or on uncleared bits.  The following patch clears the mode bits
before setting the new mode.  I've also modified it to use the appropriate
defines from pxa-regs.h for readability.

Signed-off-by: Justin Clacherty <justin@redfish-group.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>