S2IO: Removing 3 buffer mode support from the driver

 - Removed 3 buffer mode support from driver - unused feature
 - Incorporated Jeff Garzik's comments on elimination of inline typecasting
 - Code cleanup : Removed a few extra spaces

Signed-off-by: Veena Parat <veena.parat@neterion.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>