Don't enable rm2fb if it fails to start

[Eeems]

This is to try to keep the device from ending up in a bad state when users install it on an OS version that isn't supported.

[warewolf]

Looks like it worked as Eeems intended:

reMarkable: ~/ opkg install $PWD/display_1_0.0.31-2_rm2.ipk rm2fb-client_1_0.0.31-2_rm2.ipk 
Installing display (1:0.0.31-2) to root...
Installing xochitl (0.0.0-14) to root...
Downloading https://toltec-dev.org/stable/rmall/xochitl_0.0.0-14_rmall.ipk
Installing display (1:0.0.31-2) to root...
Installing rm2fb-client (1:0.0.31-2) to root...
Package rm2fb-client (1:0.0.31-2) installed in root is up to date.
Configuring xochitl.
Created symlink /etc/systemd/system/sync.service → /dev/null.
Created symlink /etc/systemd/system/multi-user.target.wants/manual-sync.service → /etc/systemd/system/manual-sync.service.
Configuring display.
Created symlink /etc/systemd/system/multi-user.target.wants/rm2fb.service → /lib/systemd/system/rm2fb.service.
Job for rm2fb.service failed because the control process exited with error code.
See "systemctl status rm2fb.service" and "journalctl -xe" for details.
Removed /etc/systemd/system/multi-user.target.wants/rm2fb.service.
Failed to start rm2fb. Keeping it disabled for now.
Please check the logs and open an issue:
  https://github.com/toltec-dev/toltec/issues/new
Configuring rm2fb-client.
Collected errors:
 * pkg_run_script: package "display" postinst script returned status 1.
 * opkg_configure: display.postinst returned 1.
reMarkable: ~/