[POWERPC] PS3: Move vuart declarations to ps3.h

Move the structures and routines needed for PS3 vuart port device registration
to asm-powerpc/ps3.h.

Signed-off-by: Geoff Levand <geoffrey.levand@am.sony.com>
Acked-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>