[POWERPC] PS3: System manager re-work

PS3 sys-manager updates to reflect the new PS3 unifed device support.
Fixups to the PS3 sys-manager driver to properly support sys_reboot().
 - Add varable request_tag to struct ps3_sys_manager_header.
 - Move ctrl_alt_del from PS3_SM_EVENT_POWER_RELEASED to
   PS3_SM_EVENT_POWER_PRESSED.
 - Make the PS3 sys-manager driver a loadable module.
 - Add new file sys-manager-core.c.
 - Add new struct ps3_sys_manager_ops for dynamic binding.
 - Put data sent to device on stack.
 - Add support for PS3_SM_SERVICE_ID_REQUEST_ERROR.

Signed-off-by: Geoff Levand <geoffrey.levand@am.sony.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>