Remove possible_crtcs and possible_clones workarounds
This is about the function
It works around
possible_clones being unreliable. If the kernel gets fixed to report realistic values, remove the workarounds.
However, if Weston gains support for atomic modesetting's
TEST_ONLY commits and iterates over possible configurations to find one that works, then it might not be necessary to use the values, if not for optimizing out definitely invalid configurations.