Add OPAL_INVALID_CALL to opal.h
Add OPAL_INVALID_CALL to opal.h

Never used, but exists for testing.

Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

legoater/skiboot,cyrilbur-ibm/skiboot,ddstreet/skiboot,jk-ozlabs/skiboot,stewart-ibm/skiboot,stewart-ibm/skiboot,shenki/skiboot,csmart/skiboot,legoater/skiboot,shenki/skiboot,open-power/skiboot,shenki/skiboot,csmart/skiboot,open-power/skiboot,qemu/skiboot,legoater/skiboot,qemu/skiboot,shenki/skiboot,neelegup/skiboot,apopple/skiboot,jk-ozlabs/skiboot,open-power/skiboot,apopple/skiboot,neelegup/skiboot,qemu/skiboot,neelegup/skiboot,qemu/skiboot,stewart-ibm/skiboot,mikey/skiboot,ddstreet/skiboot,jk-ozlabs/skiboot,cyrilbur-ibm/skiboot,open-power/skiboot,ddstreet/skiboot,open-power/skiboot,shenki/skiboot,csmart/skiboot,apopple/skiboot,qemu/skiboot,cyrilbur-ibm/skiboot,legoater/skiboot,mikey/skiboot,mikey/skiboot,legoater/skiboot