[POWERPC] EEH failure to mark pci slot as frozen.

Bug fix: when marking a slot as frozen, we forgot to mark
pci device itself as frozen. (we did manage to mark the
pci children, but forget the parent itself.)

This is needed so that some device drivers can check the
pci status in critical sections (e.g. in spin loops with
interrupts disabled).

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>