PS3: gelic: Add endianness macros

Mark the members of the structure for DMA descriptors with proper endian
annotations and use the appropriate accessor macros.
As the gelic driver works only on PS3, all these macros will be
expanded to null.

Signed-off-by: Masakazu Mokuno <mokuno@sm.sony.co.jp>
Signed-off-by: Jeff Garzik <jeff@garzik.org>