[POWERPC] PS3: Add DABR support

Add PS3 support for the PowerPC processor's Data Address Breakpoint Register
(DABR).

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