Disable PSERIES in petitboot kernel

Saves about 170kb:
-rwxr-xr-x 1 stewart users 14218342 Aug 18 15:58 zImage.epapr
-rwxr-xr-x 1 stewart users 14046310 Aug 18 16:15 zImage.epapr

The only place pseries is used is in petitboot-tests, so we
*should* be okay to disable this

Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
1 file changed