Give pi user rt permission and mlock permission

Otherwise, the user can't map and lock all memory like we want.

Change-Id: I15eaa85670123b48870db8ff64cfc80e6ff887e5
diff --git a/y2020/vision/rootfs/modify_rootfs.sh b/y2020/vision/rootfs/modify_rootfs.sh
index 289da9a..6ebeeca 100755
--- a/y2020/vision/rootfs/modify_rootfs.sh
+++ b/y2020/vision/rootfs/modify_rootfs.sh
@@ -77,6 +77,7 @@
 sudo cp sctp.conf "${PARTITION}/etc/sysctl.d/sctp.conf"
 sudo cp change_hostname.sh "${PARTITION}/tmp/change_hostname.sh"
 sudo cp frc971.service "${PARTITION}/etc/systemd/system/frc971.service"
+sudo cp rt.conf "${PARTITION}/etc/security/limits.d/rt.conf"
 
 target /bin/mkdir -p /home/pi/.ssh/
 cat ~/.ssh/id_rsa.pub | target tee /home/pi/.ssh/authorized_keys