[POWERPC] Fix typo #ifdef -> #ifndef

fpi->cp_command should be overwritten only if CONFIG_PPC_CPM_NEW_BINDING
is NOT set. Otherwise it is already set from the device tree.

Signed-off-by: Jochen Friedrich <jochen@scram.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Vitaly Bordug <vitb@kernel.crashing.org>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>