tests/util: Add `nvidia-drm` module to probe list

Whenever util_open() is called to find the first matching module, it will skip the nvidia_drm kernel module. By adding it to the list anyone with an Nvidia GPU installed (and modesetting enabled) should now see the connectors, planes etc.

Perhaps in the future we should switch over to directly open()ing /dev/dri/cardX or /dev/char/226:X, which is much easier to iterate through (that is after all what drmOpenByName() is doing internally, followed by a string match on the module name) and allows operations like modetest -c to print all the connectors instead of stopping after the first driver. It would also get rid of this redundant list that could unnecessarily go out of sync/date? A random search for the error shows that this was also attempted in (a fork of?) kmscube: https://git.ti.com/cgit/glsdk/kmscube/commit/?id=456cabc661caac5c60729751d45efd668faa8e97