[PATCH] ppc32: Fix string comparing in platform_notify_map

Fixed odd function behavior when dev->bus_id does not contain '.' - it
compared that case 0 characters of the string and hereby reported success and
executed callback. Now bus_id's are compared correctly, extra callback
triggering eliminated.

Signed-off-by: Vitaly Bordug <vbordug@ru.mvista.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>