Update file permissions

New scripts have updated executable permissions to be consistent with
project requirements.

Signed-off-by: Agathiyan Bragadeesh <agabra02@e127300.arm.com>
diff --git a/scripts/gitignore_add_generated_files.sh b/scripts/gitignore_add_generated_files.sh
old mode 100644
new mode 100755
diff --git a/scripts/gitignore_remove_generated_files.sh b/scripts/gitignore_remove_generated_files.sh
old mode 100644
new mode 100755