opal-prd: split prd message reading from handling
opal-prd: split prd message reading from handling

Signed-off-by: Jeremy Kerr <68a658b44bbaefab3ef5cd231967195fc0ff9d69@ozlabs.org>
Reviewed-by: Vasant Hegde <a6d753843573f7bfed5075c1e875b0be8007a0ab@linux.vnet.ibm.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

qemu/skiboot,shenki/skiboot,open-power/skiboot,stewart-ibm/skiboot,open-power/skiboot,open-power/skiboot,mikey/skiboot,open-power/skiboot,shenki/skiboot,legoater/skiboot,stewart-ibm/skiboot,mikey/skiboot,legoater/skiboot,qemu/skiboot,legoater/skiboot,shenki/skiboot,legoater/skiboot,qemu/skiboot,legoater/skiboot,qemu/skiboot,mikey/skiboot,stewart-ibm/skiboot,qemu/skiboot,shenki/skiboot,shenki/skiboot,open-power/skiboot