Add skiboot-5.4.2 release notes
Add skiboot-5.4.2 release notes

Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>
(cherry picked from commit 6ed71166d3d02400c2e315923f2bc6953349d7f6)
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

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