gitignore: Add Secure/Trusted Boot build files
gitignore: Add Secure/Trusted Boot build files

Signed-off-by: Michael Neuling <7b0ab45a730e48a69239010b5b8fe5fa4e8eaac6@neuling.org>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

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