Mutex/display init tweaks

Small tweaks to mutex allocation and display initialization. For the display part I had a few more patches on top, but I'm unable to test it properly as display is giving a lot of warnings on my DG2 systems. And I also couldn't finish detangling the display init sequency and header deps yet. While the rest of the patches is not ready, these 2 are simple enough to go in by themselves.

https://lore.kernel.org/intel-xe/20230225002138.1759016-1-lucas.demarchi@intel.com