If you already installed the ICS 4.0.4 I9100XXLQ5 on your Samsung Galaxy S2 and wanted to root it, here's the method that works. I'm, still waiting for chainfire's CF-root to be release porbably sooner, but for a while I already rooted mine and definitely will also root your Galaxy s2 with installed ICS 4.0.4 I9100XXLQ5 in no time.
You can root the phone via CWM method:
I use this attached zip with the lastest busybox because the one of the thread its outdated and doesn't work with chainfire cf root (wifi dont connect) if you switch to this kernel, however there is no other easy way to root XXLQ5 now.
1.- put both files on your external sd card(you must have one)
2.- shut off the phone and then press home+vol up+power
3.- once your in stock recovery select apply update from external sd card
4.- select CWM and choose yes, wait to CWM recovery appears
5.- use the touch recovery, button don't work and select flash zip from internal sd card (its inverses) select su-busybox installer reboot and done, your rooted
Biggest thanks to iNeri for confirming that this rooting method works on I9100XXLQ5 via XDA-developer.
For CF-ROOT fans out there, just keep an eye of I9100XXLQ5 root kernel via chainfire's thread.